Plasma FSH Concentrations Research Articles

Effects of breed on kinetics of ovine FSH and ovarian response in superovulated sheep

Embryo production is a useful tool for ex situ conservation of endangered species and breeds, despite a high variability in the ovarian response to superovulatory treatments. The current study evaluated the incidence and mechanisms of genetic factors in such variability, by determining the pharmacokinetics and pharmacodynamics of a standard treatment with ovine FSH (oFSH) in two endangered Spanish sheep breeds (Rubia del Molar, R, and Negra de Colmenar, N) in comparison to Manchega ewes (M, control group). In the first experiment, pharmacokinetics of an i.m. single dose of 1.32mg of oFSH was evaluated in seven animals of each breed. Plasma FSH concentrations reached their maximum at 4h post-administration in all the ewes, but several of the kinetic parameters (plasma FSH concentration at 4h post-administration, maximum plasma FSH concentration, Cmax, and both the area under the plasma concentration-time curve extrapolated to the infinite, AUCinf, and to the last moment of sampling, AUClast) were higher in the N group. In the second trial, 10 animals of each breed were superovulated using eight decreasing doses of oFSH (3× 1.32mg, 2× 1.10mg, and 3× 0.88mg). The R group, when compared to N and M, showed both a higher number of corpora lutea (13.7±0.6 versus 10.0±0.4 in N and 9.8±0.6 in M, P<0.05 for both) and embryos (7.9±0.8 versus 4.3±0.4 in N, P<0.05, and 6.7±0.5 in M, n.s.). Evaluation of pharmacokinetic and dynamic parameters showed that, although there was a trend for a higher hormone availability in R sheep, mean FSH plasma concentrations were similar between breeds (0.54±0.08ng/ml for R, 0.45±0.05ng/ml for N and 0.35±0.05ng/ml for M). However, differences were found in the number of preovulatory follicles growing in response to the FSH treatment between R (24.4±2.2), M (18.9±1.5, n.s.) and N sheep (14.1±1.4; P<0.01). Thus, differences in embryo yields between breeds would be related to differences in the pattern of follicular growth in response to FSH treatment.

Effects of chronic exposure to sodium arsenite on hypothalamo-pituitary-testicular activities in adult rats: possible an estrogenic mode of action.

BackgroundInorganic arsenic is a major water pollutant and a known human carcinogen that has a suppressive influence on spermatogenesis and androgenesis in male reproductive system. However, the actual molecular events resulting in male reproductive dysfunctions from exposure to arsenic remain unclear. In this context, we evaluated the mode of action of chronic oral exposure of sodium arsenite on hypothalamo-pituitary- testicular activities in mature male albino rats.MethodsThe effect of chronic oral exposure to sodium arsenite (5 mg/kg body weight/day) via drinking water without or with hCG (5 I.U./kg body weight/day) and oestradiol (25 micrograms oestradiol 3-benzoate suspended in 0.25 ml olive oil/rat/day) co-treatments for 6 days a week for 4 weeks (about the duration of two spermatogenic cycle) was evaluated in adult male rats. Changes in paired testicular weights, quantitative study of different varieties of germ cells at stage VII of spermatogenic cycle, epididymal sperm count, circulatory concentrations of hormones (LH, FSH, testosterone and corticosterone), testicular activities of delta 5, 3beta-hydroxysteroid dehydrogenase (delta 5, 3beta-HSD), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), sorbitol dehydrogenase (SDH), acid phosphatase (ACP), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH), as well as the levels of biogenic amines (dopamine, noradrenaline and 5-hydroxytryptamine (5-HT)) in the hypothalamus and pituitary were monitored in this study. Hormones were assayed by radioimmuno- assay or enzyme- linked immunosorbent assay and the enzymes were estimated after spectrophotometry as well as the biogenic amines by HPLC electrochemistry.ResultsSodium arsenite treatment resulted in: decreased paired testicular weights; epididymal sperm count; plasma LH, FSH, testosterone and testicular testosterone concentrations; and increased plasma concentration of corticosterone. Testicular enzymes such as delta 5, 3 beta-HSD, 17 beta-HSD, and sorbitol dehydrogenase (SDH) were significantly decreased, but those of acid phosphatase (ACP), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) were significantly increased. A decrease in dopamine or an increase in noradrenaline and 5-HT in hypothalamus and pituitary were also noted after arsenic exposure. Histological evaluation revealed extensive degeneration of different varieties of germ cells at stage VII of spermatogenic cycle in arsenic exposed rats. Administration of human chorionic gonadotrophin (hCG) along with sodium arsenite partially prevented the degeneration of germ cells and enhanced paired testicular weights, epididymal sperm count, plasma and intratesticular testosterone concentrations, activities of delta 5, 3beta-HSD, 17 beta-HSD and sorbitol dehydrogenase along with diminution in the activities of ACP, ALP and LDH. Since many of the observed arsenic effects could be enhanced by oestradiol, it is suggested that arsenic might somehow acts through an estrogenic mode of action.ConclusionThe results indicate that arsenic causes testicular toxicity by germ cell degeneration and inhibits androgen production in adult male rats probably by affecting pituitary gonadotrophins. Estradiol treatment has been associated with similar effects on pituitary testicular axis supporting the hypothesis that arsenite might somehow act through an estrogenic mode of action.

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10 mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, α-MSH, and TSH were collected at −15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation. MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for FSH after suprapituitary stimulation were significantly higher before treatment than at 5, 8, and 11 months of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and α-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH. In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic–pituitary–adrenocortical axis, and unaffected secretion of prolactin and α-MSH.

Changes in Circulating and Testicular Levels of Inhibin A and B During Postnatal Development in Bulls

We investigated testicular and circulating levels of dimeric inhibins in Holstein bulls from the infantile to postpubertal periods (5 to 50 weeks of age) and examined the relationship between the profiles of circulating dimeric inhibins and FSH. Concentrations of total inhibin and inhibin B in the testis were highest at 4 to 5 weeks of age but decreased gradually as the bulls aged. Testicular inhibin A levels showed a gradual decline to a nadir at 15 to 26 weeks of age, but by 39 weeks, they were high again. The contents of total inhibin, inhibin A, and inhibin B per testis generally increased with age. Fractionation of testicular homogenates obtained from 15-week-old bulls by a combination of immunoaffinity chromatography and SDS-PAGE confirmed the presence of two major molecular weight forms (32 and 45 kDa) of dimeric inhibins in the testes. Circulating levels of total inhibin and inhibin A showed a significant increase in bulls at around 10 to 14 weeks of age compared to the levels between 5 and 7 weeks of age but decreased thereafter. However, immunoreactivity for inhibin B was not detected in the peripheral circulation, probably because of low sensitivity of the inhibin B assays. The concentrations of plasma FSH were high at 5 weeks of age but declined to lower levels between 11 and 40 weeks, and then increased from 41 weeks onward. There was no significant correlation between the plasma levels of FSH and inhibin A or total inhibin. The results clearly indicate that the bull testis produces inhibin A and B and secretes at least inhibin A into the circulation during postnatal development. However, the profile of circulating FSH in bulls shows no reciprocal relationship with the inhibin A or total inhibin profile during the postnatal period.

Effects of Bilateral Efferent Duct Ligation on Sperm Motility and Secretion of FSH, LH, Inhibin, and Testosterone in Adult Male Rats

Effects of bilateral efferent duct ligation (EDL) on sperm motility and testicular endocrinology were investigated in adult male rats. Bilateral EDL was created surgically in adult male rats (EDL group) and shamoperated rats were used as control (control group). Five rats from each group were killed on d 3, 5, 7, 14, and 35 after the surgery. The sperm motility parameters were determined by a computer-assisted sperm analysis system using sperm collected from the cauda epididymis. Concentrations of spermatozoa in epididymis and testis were counted. The motility of sperm decreased remarkably in EDL rats compared with controls on 5 d after the operation. Four sperm motility parameters-straight velocity (VSL), deviation of the sperm head from the mean trajectory (ALH, mean), the maximum amplitude of lateral head displacement (ALH, max) and curvilinear velocity (VCL)-increased on 3 d after the operation, and followed by a subsequent decline 5 and 7 d later. Concentrations of sperm significantly decreased in both testes and epididymis from 3 and 5 d after the operation. Plasma concentrations of FSH and LH increased significantly in EDL rats from 5 and 7 d after the operation, whereas plasma concentrations of immunoreactive (ir)-inhibin, inhibin B, and testosterone decreased. Testicular content of irinhibin showed an initial increase on 3 d after the operation, followed by a subsequent decline to levels significantly below controls by d 7 postoperation. On the other hand, testicular contents of testosterone were significantly higher in the EDL group than the control group on d 7-35 after the operation, whereas circulating levels of testosterone remained low. In the EDL testes, marked degenerative changes in the Sertoli cells and spermatogonia were observed, whereas Leydig cells showed clear hyperplasia. These results demonstrated that bilateral EDL induced a rapid reduction of sperm motility parameters during a short time. Present results also suggest that EDL first induces impairment of Sertoli cells function and this leads to reduction of sperm activity and secretion of inhibins. On the other hand, circulating levels of testosterone reduced after EDL and this leads to hypersecretion of LH. A large amount of LH resulted in a stimulation of Leydig cells hyperplasia.

Immunization of Goats against Inhibin Increased Follicular Development and Ovulation Rate

In the present study, two experiments were conducted to induce superovulation in goats using passive and active immunization against inhibin. In the first experiment, two groups of goats were given an intravenous injection of either 10 ml normal goat serum (control; n=6) or inhibin antiserum developed against [Tyro30]-inhibin alpha (1-30) (passively immunized; n=6) 48 h before treatment with PGF2alpha. In the second experiment, two groups of goats were immunized with inhibin vaccine (actively immunized; n=5) or Freund's adjuvant (control; n=5) followed by three booster immunizations at 4 week intervals. Blood samples were collected for determination of FSH, LH, estradiol-17beta, and progesterone. Ultrasonography was used to determine ovarian activity at PGF2alpha injection and ovulation rate one week after estrus. In both experiments, there was a significant increase in plasma FSH concentration compared with the controls. However, the pattern of the FSH levels was different between the passively and actively immunized goats. The numbers of follicles in passively and actively immunized goats (22.4 +/- 2.3 and 18.6 +/- 2.1, respectively) were significantly greater than those in the controls (2.6 +/- 0.4 and 2.3 +/- 0.4, respectively). In addition, the ovulation rate was greater in the immunized animals compared with the controls. Therefore, either passive or active immunization against inhibin could be used to induce superovulation in goats.

Seasonal changes in semen characteristics, hormonal profiles and testicular activity in Zaraibi goats

Ten Zaraibi buck goats were used to study the effect of season on semen quality. Bucks were housed and fed according to standard recognized practices. Semen was collected twice a week for 7 consecutive weeks (starting from the 3rd to the 9th week) in the mid of the each season. During these periods scrotal circumference was measured fortnightly. The number of mounts terminating in ejaculation and the time interval between the first mount and ejaculation were also recorded. The physical parameters of semen and semen index (semen volume × spermatozoa concentration/ml × live spermatozoa% × progressive motility%) were measured for the first and the second ejaculates of each semen collection during the week. At the end of each season, testicular biopsies were obtained surgically from three bucks for histological evaluation. Plasma testosterone, FSH and LH concentrations were also determined twice weekly. Bucks demonstrated the highest libido in summer, using the least ( P < 0.01) number of mounts and a shorter ( P < 0.01) reaction time. This coincided with a higher ( P < 0.01) level of plasma testosterone (10 ng/ml) and the best semen quality (semen index: 3354 × 10 6). During autumn, bucks recorded the highest ( P < 0.01) ejaculate volume (0.98 ml) and the maximum output of sperm (4565 × 10 6), as well as a lower ( P < 0.01) percentage of sperm abnormalities (8.8%). This was accompanied by high concentrations of plasma LH (average 2.9 mIU/ml). The histological structure of the testis indicated that during autumn (natural breeding season) seminiferous tubules (Sta) occupied the majority of the testicular tissues (76.6%) and the spermatic layers were highest. It can be said that Zaraibi bucks have distinct seasonal activity, with poor semen characteristics during winter and spring—which may be a critical obstacle for implementing intensive systems of three kidding in 2 years when natural mating is applied.

Reducing Estrogen Synthesis Does Not Affect Gonadotropin Secretion in the Developing Boar1

Boars have high concentrations of plasma and testicular estrogens, but how this hormone is involved in feedback regulation of the gonadotropins and local regulation of testicular hormone production is unclear. The present study examined the effects of reducing endogenous estrogens by aromatase inhibition on concentrations of plasma LH and FSH and on testicular and plasma concentrations of testosterone (T) and immunoreactive inhibin (INH). Thirty-six littermate pairs of boars were used. One boar from each pair was assigned to the control group (vehicle); the other boar to the treatment group (aromatase enzyme inhibitor, Letrozole, 0.1 mg/kg body weight [BW]). Weekly oral treatment started at 1 wk of age and continued until castration at 2, 3, 4, 5, 6, 7, or 8 mo. Plasma concentrations of gonadotropins, INH, T, estradiol (E2), and estrogen conjugates (ECs) were determined. Testicular tissue was collected at castration for determination of INH and T and for confirmation of reduced aromatase activity. The acute effects of aromatase inhibition on gonadotropins were monitored in two adult boars treated once with Letrozole (0.1 mg/kg BW). Treatment with the aromatase inhibitor reduced testicular aromatase activity by 90% and decreased E2 and ECs without changing acute, long-term, or postcastration LH and FSH. Plasma T, testicular T, and circulating INH concentrations did not change. Testicular INH was elevated in treated boars compared with controls. In conclusion, estrogen does not appear to play a regulatory role on gonadotropin secretion in the developing boar. This is in direct contrast to findings in males of several other species.

Effects of early prenatal exposure to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) on postnatal reproduction in the laying hen ( Gallus gallus)

This study demonstrates the long-term effects of very early embryonic exposure to a single dose of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) (0, 10 and 20 ng/egg), administered before the beginning of embryonic development, on growth and reproductive performance in laying hens. Hatchability and body weight gain from 11 weeks onwards were significantly depressed in 20 ng treated hens. All hens started laying egg at around the same age and the laying performance of TCDD-treated hens was normal. No disturbances in the age-related pattern and concentrations of oestradiol, LH or FSH in plasma could be found but mean progesterone concentrations were significantly lower in 20 ng treated hens. Moreover, follicular distribution was changed with less small white follicles and smaller yellow follicles, which probably resulted in the lower egg weight of the 20 ng treated hens. At 43 weeks of age, hens treated in ovo with TCDD showed a retained right oviduct, mostly filled with clear fluid. From these results, it seems that in ovo exposure to TCDD interferes in the right oviduct regression during embryonic development and induces some changes in follicular distribution but without impairment of reproductive performance in the adult laying hen.

Effect of active immunization against inhibin on hormonal concentrations and semen characteristics in Shiba bucks

Active immunization against inhibin increased ovulation rate in females; in males, the effects of active immunization against inhibin on hormonal concentrations and sperm production need more investigation. To test the hypothesis that active immunization against inhibin increases FSH secretion and sperm output, the present study was undertaken to determine the effects of active immunization against inhibin on hormonal profile and sperm production in Shiba bucks. The bucks were actively immunized against inhibin α-subunit (immunized group, n = 6) or Freund adjuvant (control group, n = 5) four times, at 5-weeks intervals. Blood samples were collected twice-weekly and two successive ejaculates of semen were collected (with an artificial vagina) once-weekly. Plasma concentrations of FSH, LH and testosterone were measured by radioimmunoassay (RIA) and sperm motility characteristics were measured by computer-assisted sperm analysis (CASA). All inhibin-immunized bucks produced antibodies against inhibin. Relative to control bucks, in immunized bucks there were significant increases in plasma FSH concentrations and in sperm concentrations from 5 to 9 weeks and from 8 to 11 weeks, respectively, after primary immunization. However, plasma concentrations of LH and testosterone, semen volume, percentage of motile spermatozoa and motility parameters (straight-line velocity, curvilinear velocity and linearity index) were similar in both groups. In conclusion, active immunization against inhibin α-subunit increased FSH secretions and enhanced sperm production in bucks, whereas LH and testosterone concentrations, semen volume and sperm motility parameters were unaffected. Active immunization against inhibin could be used to improve fertility in Shiba bucks.

Effect of litter separation on 24-hour rhythmicity of plasma prolactin, follicle-stimulating hormone and luteinizing hormone levels in lactating rabbit does

BackgroundThis work describes the effect of a 48-h litter separation on 24-h patterns of plasma prolactin, FSH and LH concentration in female lactating rabbits kept under a 16:8 light-dark photoperiod (lights on at 0800 h).MethodsGroups of 6–7 female lactating rabbits maintained with their litters or separated from them for 48 h were killed by decapitation on day 11 post-partum, at 6 different time points throughout a 24-h cycle, starting at 0900 h. Plasma levels of prolactin, FSH and LH were measured by specific double antibody radio-immunoassays.ResultsPlasma level of prolactin in control and separated does changed in a similar way throughout the day, showing two maxima, at 0500–0900 h and at 1700–2100 h, respectively. Litter separation significantly augmented plasma FSH and LH and disrupted their 24-h rhythmicity.ConclusionSince previous studies had shown that litter separation for short periods of time augmented sexual receptivity and fertility of the doe, the changes in FSH and LH reported may influence the massive release of gonadotropin releasing hormone, LH and FSH triggered by mating or artificial insemination in litter-separated mothers.

Alterations in follicular dynamics and steroidogenic abilities induced by heat stress during follicular recruitment in goats

We investigated the changes in follicular dynamics and steroidogenic activity during heat stress in goats. Adult female goats were exposed to heat stress at 36 degrees C and 70% relative humidity for 48 h and then injected with prostaglandin (PG) F2alpha (the time of PGF2alpha injection was designated as 0 h). In experiment 1, every follicle greater than 2 mm in diameter was monitored by ultrasonography to investigate the follicular dynamics, and plasma concentrations of FSH, LH, progesterone, and oestradiol were measured from -48 h to 120 h. In experiment 2, the follicles were recovered from the goats at 48 h, and the concentration of oestradiol, the aromatase activity, and the LH receptor level in the follicles were determined. In control (non-heat-stressed) goats, ovulatory follicles were mainly recruited from -24 h to 0 h, whereas no follicles recruited during that period were ovulated in the heat-stressed goats. The timing of the recruitment of ovulatory follicles was delayed by heat stress by approximately 24 h. The plasma concentration of oestradiol in the heat-stressed goats was significantly lower from 36 to 54 h compared with the controls, although the concentrations of FSH and progesterone did not differ between the treatments. In addition, the concentration of oestradiol, the aromatase activity, and the LH receptor level in the follicles from heat-stressed goats were significantly lower compared with the controls. These results indicate that heat stress during follicular recruitment suppresses subsequent growth to ovulation, accompanied by decreased LH receptor level and oestradiol synthesis activity in the follicles.

Short-term nutritional supplementation of ewes in low body condition affects follicle development due to an increase in glucose and metabolic hormones

This study tested whether the effects of a short period of nutritional supplementation given to ewes during the luteal phase on follicle development and ovulation rate is associated with an increase in circulating concentrations of FSH, glucose or metabolic hormones. Oestrus was synchronised with two prostaglandin injections given 9 days apart and the supplement consisted of corn grain and soybean meal. Corriedale ewes with low body condition were randomly assigned to 2 groups: the control group (C; n = 10) received a maintenance diet while the short-term supplemented group (STS; n = 10) received double the maintenance diet over days 9 to 14 of the oestrous cycle (day 0 = ovulation). Ovaries were examined daily by ultrasound and blood was sampled three times a day during the inter-ovulatory interval for measuring reproductive and metabolic hormones. On days 9, 11 and 14 of the oestrous cycle, half of the ewes from each group (n = 5) were bled intensively to determine the concentrations of glucose, insulin, IGF-I and leptin. Plasma FSH, progesterone, oestradiol and androstenedione concentrations were similar among groups. Dietary supplementation increased plasma insulin concentrations from the first to the sixth day of supplementation and increased glucose concentrations on the third day, compared with control ewes. Plasma leptin concentrations were higher in STS ewes from the second to the fifth day of supplementation. The pattern of IGF-I concentrations was similar among groups. In STS ewes, the nutritional treatment prolonged the lifespan of the last non-ovulatory follicle, so fewer follicular waves developed during the cycle. In STS ewes, increased concentrations of glucose, insulin and leptin one day before ovulatory wave emergence were associated with increased numbers of follicles growing from 2 to 3 mm and with stimulation of the dominant follicle to grow for a longer period. We suggest that the mechanism by which short-term nutritional supplementation affects follicle development does not involve an increase in FSH concentrations, but may involve responses to increased concentrations of glucose, insulin and leptin, acting directly at the ovarian level. This effect is acute, since concentrations of all three substances decrease after reaching peak values on the third day of supplementation. The status of follicle development at the time of maximum concentrations of glucose and metabolic hormones may be one of the factors that determines whether ovulation rate increases or not.

Induction of Superovulation by Immunoneutralization of Endogenous Inhibin in Immature Rats

The effects of passive immunoneutralization of endogenous inhibin on ovulation rate in immature rats were investigated. Efficiency of superovulation on production of fertilized oocytes was compared between the inhibin antiserum (inhibin-AS) and equine chorionic gonadotropin (eCG) protocols. Immature female Wistar strain rats were superovulated with a single injection of 100-200 microl inhibin-AS, with and without an injection of human chorionic gonadotropin (hCG). A total of 77.8% of the 26-30-day-old rats treated with a single injection of 100-200 microl inhibin-AS ovulated 72 h after treatment, while rats given normal goat serum (NGS; 200 microl) did not ovulate. At 28 days of age, all of the inhibin-AS treated rats ovulated when additional hCG treatment was given, whereas the number of ovulated oocytes was not affected. The number of ovulated oocytes in the inhibin-AS-hCG treated groups was significantly higher than that of the NGS-hCG treated group. In addition, plasma concentrations of FSH in the inhibin-AS-hCG treated group significantly increased compared with the NGS treated group. While the percentage of mated rats in the 200 microl inhibin-AS-hCG treated group was significantly lower than that of the 15 IU eCG-hCG treated group, the fertilization rate was comparable between the two groups. The number of fertilized oocytes in the 200 microl inhibin-AS-hCG treated group was significantly higher in comparison with the 15 IU eCG-hCG treated group. These results suggest that immunoneutralization of endogenous inhibin could be a reliable method for induction of superovulation to collect a large number of normally fertilized oocytes in immature rats.

Secretion of Inhibin and Testicular Expression of Inhibin Subunits in Male Duck Embryos and Newly Hatched Ducks

Concentrations of immunoreactive (ir-) inhibin in circulation, amniotic fluid, and testes of embryos and newly hatched ducks were determined from d 21 of incubation to d 1 of age. Plasma concentrations of FSH and LH were also determined by chicken radioimmunoassay (RIA) systems. In addition, gene expression and cellular source of inhibin were investigated by in situ hybridization and immunohistochemistry. The results showed that plasma ir-inhibin gradually declined from d 21 to d 24, followed by an increase on d 25 and remained high until d 1 after hatching. FSH in plasma was high on d 21 followed by a sharp decline toward d 25 after which FSH levels stabilized. A reverse relationship was observed between inhibin and FSH during the late stage of incubation. Embryonic testes contained high ir-inhibin levels. Testicular ir-inhibin levels were relatively high at early time points with a peak on d 23, and significantly decreased from d 23 to d 24 and stabilized thereafter. Amniotic fluid concentrations of ir-inhibin were relatively low and remained constant between d 21 and d 25. In situ hybridization demonstrated that the expression of inhibin alpha- and betaA-subunit mRNA was coexisted in the cells in the seminiferous tubules of testes on d 25. The immunoreactivity of inhibin betaA- and betaB-subunits was colocalized in the cells in the seminiferous tubules of testes on d 25. The results of dimeric inhibins determined by the ELISA method showed that inhibin B can be measured in embryonic testicular homogenate and pooled embryonic plasma. Although inhibin A was detected in testicular homogenate, it was under the detection limit in pooled embryonic plasma. In conclusion, these results indicate that cells in the seminiferous tubules of embryonic testes in ducks may secrete dimeric (bioactive) inhibins to circulation and that the FSH-inhibin feedback loop may become operational during the late stage of the incubation.

Follicular and Hormonal Dynamics during the Estrous Cycle in Goats

Transrectal ultrasonography of ovaries was performed daily in 6 goats for 3 consecutive estrous cycles. Blood samples collected daily were measured for concentrations of FSH, inhibin A, and estradiol-17beta. Follicular and hormonal data were analyzed for associations between the follicular waves and hormonal concentrations. During the interovulatory intervals, follicular growth and regression occurred in a wave like pattern (2-5 waves), and the predominant patterns were three and four follicular waves. In addition, there was no significant difference among the diameters of dominant follicles during the growth phase of the follicular waves. The number of 3 mm follicles peaked on days 0, 7, and 11 in interovulatory intervals that had three follicular waves and on days -1, 5, 11, and 15 in those that had four follicular waves. Plasma concentrations of FSH increased around the day of follicular wave emergence and declined with the growth of follicles. Circulating FSH increased again concomitant with regression of dominant follicles in the anovulatory wave, whereas FSH levels remained low in the ovulatory wave. Inhibin A was negatively correlated with FSH, while it was positively correlated with estradiol-17beta, suggesting that inhibin A is a product of healthy growing follicles and that it contributes to the suppression of FSH secretion. In conclusion, the growth of ovarian follicles in goats exhibits a wave-like pattern, and follicular dominance is less apparent in goats. Moreover, inhibin A may be a key hormone for regulation of the follicular wave through suppression of FSH secretion in goats.

Effects of oestradiol and some of its esters on gonadotrophin release and ovarian follicular dynamics in CIDR-treated beef cattle

Three experiments were conducted to: (1) compare the effect of three oestradiol formulations on gonadotrophin release in ovariectomised cows; (2) compare the effects of either oestradiol-17β (E-17β) or oestradiol benzoate (EB), given at two doses, on the synchrony of ovarian follicular wave emergence in CIDR-treated beef cattle; and (3) determine the timing of ovulation of the dominant follicle of a synchronised follicular wave following administration of E-17β or EB 24 h after progesterone withdrawal. In Experiment 1, ovariectomised cows ( n = 16) received a once-used CIDR on Day 0 (beginning of the experiment) and were allocated randomly to receive 5 mg of E-17β, EB or oestradiol valerate (EV) plus 100 mg progesterone i.m. The CIDR inserts were removed on Day 7. There were effects of time, and a treatment-by-time interaction ( P < 0.0001) for plasma concentrations of both oestradiol and FSH. Plasma oestradiol concentrations peaked 12 h after treatment, with highest ( P < 0.01) peak concentrations in cows given E-17β; estradiol concentrations subsequently returned to baseline by 36 h in E-17β-treated cows and by 96 h in EB- and EV-treated cows. Plasma FSH concentrations decreased by 12 h after oestradiol treatment in all groups ( P < 0.0001), reached a nadir at 24 h, and increased by 60 h in all groups; plasma FSH reached higher ( P < 0.02) concentrations in E-17β-treated than in EB- or EV-treated cows. In Experiment 2, non-lactating Hereford cows ( n = 29) received a new CIDR on Day 0 (beginning of the experiment), and were assigned randomly to receive 1 or 5 mg of E-17β or EB i.m. on Day 1. On Day 8, CIDR were removed and PGF was given. Transrectal ultrasonography was done once daily from 2 days before CIDR insertion to 2 days after CIDR removal, and then twice-daily to ovulation. Although there was no difference among groups in the interval from oestradiol treatment to follicular wave emergence (4.2 ± 0.3 days; P = 0.5), 5 mg of E-17β resulted in the least variable interval to wave emergence ( P < 0.005), compared with the other treatment groups which were not different ( P = 0.1). For the interval from CIDR removal to ovulation, there were no differences among groups for either means ( P = 0.5) or variances ( P = 0.1). In Experiment 3, beef heifers ( n = 32) received a once-used CIDR on Day 0 (beginning of the experiment) plus 100 mg progesterone i.m. and were assigned randomly to receive 5 mg E-17β or 1 mg EB i.m. On Day 7, CIDR were removed and all heifers received PGF. On Day 8 (24 h after CIDR removal), each group was subdivided randomly to receive 1 mg of either E-17β or EB i.m. There was no effect of oestradiol formulation on interval from treatment to follicular wave emergence (4.1 ± 0.2 days; P = 0.7) or on the median interval (76.6 h; P = 0.7) or range (72–120 h; P = 0.08) from CIDR removal to ovulation. In summary, oestradiol treatments suppressed FSH in ovariectomised cows, with the duration of suppression dependent on the oestradiol formulation. Both E-17β and EB effectively synchronised ovarian follicular wave emergence and ovulation in CIDR-treated cattle, and the interval from CIDR removal to ovulation did not differ in heifers given either E-17β or EB 24 h after CIDR removal.

Effect of divergent selection for testosterone production on testicular morphology and daily sperm production in boars.

The objective of this study was to characterize correlated responses in testicular morphology and daily sperm production to divergent selection for testosterone production. Duroc boars from high and low lines (HTL and LTL, respectively) divergently selected over 10 generations for testosterone production in response to a GnRH challenge followed by random selection were used. Testicular tissues were sampled from all available males of generation 20 (HTL, n = 46; and LTL, n = 13). Volume densities for Leydig cells, seminiferous tubules, and Sertoli cells were estimated along with sperm production. The HTL boars had greater volume densities of Leydig cells than did LTL (P < 0.01). Volume density of seminiferous tubules tended to differ between lines (P < 0.07), but Sertoli cell volume densities did not differ (P < 0.27). Sperm production traits, adjusted for age, did not differ significantly between lines. Body, testicular, and epididymal weights were recorded for boars from HTL (n = 82) and LTL (n = 44) from generations 20 and 21. After adjustment for BW, average paired testicular weights for HTL and LTL were 417 and 457 g (P < 0.01), respectively. Epididymal weights, adjusted for BW, were heavier for HTL (P < 0.01) than for LTL. To demonstrate that the selection lines still differed for testosterone production, lines were evaluated in generation 21. Endogenous testosterone production of the HTL (n = 54) and LTL (n = 44) testosterone production line averaged 49.0 ng/mL and 27.8 ng/mL (P < 0.01), respectively. Plasma FSH concentrations did not differ between lines (P < 0.30). Selection for testosterone production in response to a GnRH challenge was an effective method of changing testosterone concentrations, testicular size, epididymal weight, and volume density of Leydig cells. However, daily sperm production per gram of testes was unchanged. Based on the results of this study, selection for testosterone production is not recommended as a method of increasing sperm production in pigs.

Oestradiol-17β responsiveness, plasma LH profiles, pituitary LH and FSH concentrations in long-term ovariectomised Holstein cows at 24 h, 48 h and 21 days following treatment with an absorbable GnRH agonist implant

Non-lactating OVX Holstein cows ( N = 34) were used to investigate the effect of s.c. placement of an absorbable GnRH agonist implant (Ovuplant ®; deslorelin 2.1 mg, Peptech Animal Health, Australia) on the relationship of plasma LH, oestradiol responsiveness and pituitary LH content. On the day of implant insertion (Day 0), one group (OVU-48h; N = 5) received Ovuplant ® and had blood samples collected at hourly intervals to characterize the LH response, while a second group (CON-48h; N = 5) remained untreated and acted as controls. Blood samples were collected every 10 min over 6 h from CON-48h and OVU-48h, at 24 h post-implant insertion. These cows were then slaughtered at 48 h post-implant insertion and their pituitaries recovered. Another group received Ovuplant ® (OVU-21d+E2; N = 10) or were left untreated (CON-21d+E2) and 21 days later were injected i.m. with 0.5 mg 17β-E2. Blood samples were collected every 10 min for 4 h on the day before E2 injection to characterize LH pulse frequency and amplitude. Beginning 14 h later, blood samples were collected hourly for 12 h to characterize the expected LH surge. These cows were slaughtered and their pituitary glands recovered and assayed for LH and FSH content. Peak plasma LH concentrations (59±19 ng/ml) were measured after 30 min of Ovuplant ® insertion. They had returned to pre-treatment levels by 7 h. By 24 h post-implant insertion, OVU-48h plasma LH profiles were characterized by reduced LH pulse frequency (0.23 ± 0.09 pulses/h versus 0.75 ± 0.26 pulses/h; OVU-48h versus CON-48h; P < 0.05). The cows that received Ovuplant ® had lower LH pulse amplitude, LH pulse frequency and mean LH concentrations after 20 days. Injection of 0.5 mg 17β-E2 induced an LH surge in every one of the control cows with their peak concentrations measured 18 h post injection. No increase in LH was detected in any Ovuplant ® treated cows. Pituitary FSH content was reduced in Ovuplant ® treated cows after 48 h, but not that of LH. In conclusion, absorbable deslorelin implants induced a substantial but temporary release of LH, but even 21 days later their LH profiles were characterized by marked suppression of pulsatile LH and an absence of response to E2. These results suggest the implant has prolonged biological activity.

Developmental pattern of small antral follicles in the bovine ovary.

The study was designed to characterize the developmental pattern of 1- to 3-mm follicles and to determine the stage at which the future dominant follicle first attains a size advantage among its cohorts. In experiment 1, heifers (n = 18) were examined every 24 h by transrectal ultrasonography for one interovulatory interval (IOI). In experiment 2, cows (n = 9) were examined every 6 h from 5 to 13 days after ovulation to monitor precisely the diameter changes of individual follicles >/=1 mm during emergence of wave 2. Results revealed a change over days (P < 0.05) in the number of 1- to 3-mm follicles, with a maximum (P < 0.05) 1 or 2 days before wave emergence (conventionally defined as the time when the dominant follicle is first detected at 4 mm), followed 3-4 days later by a maximum (P < 0.05) in the number of >/=4-mm follicles. The profiles of small (1-3 mm) and large (>/=4-mm) follicles were inversely proportional (r = -0.79; P = 0.01). The profile of the number of 1- to 3-mm follicles during wave emergence was similar (P = 0.63) between waves in two-wave IOI, but differed (P < 0.01) among waves in three-wave IOI as a result of a greater number of follicles in the ovulatory wave (P < 0.04). As well, the number of follicles in the ovulatory wave tended to be greater (P < 0.06) in three-wave IOI than in two-wave IOI. The future dominant follicle was first identified at a diameter of 1 mm and emerged 6-12 h earlier than the first subordinate follicle (P < 0.01). After detection of the dominant follicle at 1 mm (0 h), its diameter differed from that of the first and second subordinate follicles at 24 h (P = 0.04) and 12 h (P = 0.01), when the dominant follicle was 2.4 +/- 0.17 mm and 1.7 +/- 0.14 mm, respectively. The growth rate of the dominant follicle differed from that of the first and second subordinate follicles at 120 h (P = 0.03) and 108 h (P = 0.02), when the dominant follicle was 9.5 +/- 0.30 mm and 8.8 +/- 0.49 mm, respectively. Emergence of the future dominant (r = 0.71), first (r = 0.73), and second (r = 0.76) subordinate follicles was temporally associated (P < 0.01) with a rise in circulating concentrations of FSH. Transient, nocturnal elevations in plasma FSH concentration were followed within 6 h by an increase in the growth rate of 1- to 3-mm follicles. We conclude that 1) 1- to 3-mm follicles develop in a wave-like manner in association with surges in plasma concentrations of FSH, 2) 1- to 3-mm follicles are exquisitely responsive to transient elevations in FSH, and 3) selection of the dominant follicle is manifest earlier than previously documented and is characterized by a hierarchical progression over a period encompassing the entire FSH surge (5 days).