Peak Progesterone Concentrations Research Articles

Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes

A standard dose of 500 IU of eCG is commonly given to progestogen pre-treated anestrous ewes for induction of estrus. Twelve seasonally anestrous and 12 cyclic Western White Face ewes were treated for 12 days with intravaginal sponges impregnated with medroxyprogesterone acetate (MAP). In trials in both the breeding and nonbreeding seasons, six randomly selected ewes were given 500 IU of eCG at sponge removal to determine the effects of low dose of eCG on ovarian antral follicular dynamics and ovulation. Ultrasound scanning and blood sampling were done daily. Treatment with eCG did not have marked effects on antral follicular growth. All ewes ovulated, except for five of six control anestrous ewes. Luteal structures and progesterone secretion were confirmed in all but the control anestrous ewes. In the breeding season, peak progesterone concentrations were greater ( P<0.05) in eCG-treated compared to control ewes. Daily serum estradiol concentrations were greater in the periovulatory period in eCG-treated compared to control ewes (treatment-by-day interaction; P<0.05), particularly in anestrus. Progestogen-treated ewes ovulated follicles from several follicular waves, in contrast to ovulations of follicles from the final wave of the cycle in untreated, cyclic ewes. Anestrous ewes exhibited more frequent follicular waves and FSH peaks compared to cyclic ewes after a progestogen/eCG treatment. In conclusion, 500 IU of eCG given after 12 days of progestogen treatment had limited effects on the dynamics of ovarian follicular waves. However, eCG treatment increased serum concentrations of estradiol during the periovulatory period, particularly in anestrous ewes; this probably resulted in the synchronous estrus and ovulation in anestrous ewes.

Effect of dietary energy and protein density on body composition, attainment of puberty, and ovarian follicular dynamics in dairy heifers.

The objectives were to examine the effects of dietary energy and protein density on age and body composition at puberty, and on ovarian follicular dynamics during the pre- and peripubertal periods in Holstein heifers. In Phase 1, heifers were randomly allotted (n=10 per diet) at 100 kg body weight (BW) to diets with either low (P1L), medium (P1M) or high (P1H) energy and protein formulated for an average daily gain (ADG) of 0.5, 0.8 or 1.1 kg per day, respectively. During Phase 2 (P2), all heifers were fed ad libitum a common diet formulated for an ADG of 0.8 kg per day. Half the animals within the high (n=5) and low groups (n=5) entered P2 either at 12 months of age (P2H-12; P2L-12) or at 330 kg BW (P2H-330; P2L-330). Heifers fed P1H, P1M, P1L, and P2L-12 diets attained puberty at approximately 9, 11, 16, and 14 months of age, respectively (P<0.01). Urea space estimates of body fat and protein percent, and back-fat thickness, were lower in P1L heifers compared to P1H or P1M heifers at similar chronological ages (P<0.05) but did not differ at puberty (P>0.10). Compared to P1L heifers, P1H heifers had high amplitude LH pulses at 8 months, and high frequency low amplitude LH pulses at 10 months of age (P<0.05). The mean diameter (mm) of the dominant follicle was smaller (P<0.05) in P1L heifers (10.6) compared to P1H (12.8) or P1M (12.2) heifers at 8 months. Maximum size and growth rate of the nonovulatory dominant follicle increased with age (P<0.05) but did not differ between P1H and P1M heifers at puberty. The diameter (mm) of the nonovulatory dominant follicle, and the first and second ovulatory follicles were larger in P2L-12 heifers (14.0, 14.7, and 14.9) compared to P1M heifers (13.1, 12.5, and 11.9), while the peak progesterone levels and CL growth were lower (P<0.05) in the first cycle. In conclusion, dairy heifers attained puberty at a constant body weight and body composition independent of dietary manipulation, the size of dominant follicles increased with age in association with increased LH support, and heifers realimented from a low energy diet developed larger first ovulatory follicles and smaller CL with lower peak progesterone concentrations in the first cycle.

Late luteal rescue in the baboon (Papio cynocephalus).

Numerous studies have used human chorionic gonadotrophin (HCG) administration to study the response of the primate ovary to gonadotrophin stimulation. These studies are generally performed in the luteal phase with very few studies of the follicular phase. We have studied the effect of both HCG and gonadotrophin releasing hormone (GnRH) agonist administered at the early follicular phase in normally cycling baboons (Papio cynocephalus). Five baboons were treated with increasing doses of HCG for 5 consecutive days starting on day 1 of the cycle and three untreated baboons served as controls. Follicular and luteal phase lengths were determined and serum samples were assayed for progesterone, oestradiol and 17alpha-OH progesterone. In a separate study, six baboons were treated with GnRH agonist (WY-40972) on days 2-6 of the cycle and saline-treated baboons served as controls (n = 5). Mean peak progesterone concentrations (+/- SE) during the treatment interval were 3.88+/-0.56 ng/ml in HCG-treated baboons compared to 0.19+/-0.07 ng/ml in controls (P < 0.001). A similar significant increase (P < 0.001) in serum 17alpha-OH progesterone concentrations was also observed (6.13+/-1.12 ng/ml versus 1.13+/-0.49 ng/ml). In association with the increase in luteal steroids there was also a significant prolongation of menstrual cycle length from 32.7+/-1.2 days in controls to 46.8+/-4.9 days in HCG-treated baboons (P < 0.05), which involved prolongation of the follicular phase (16.7+/-1.2 days to 29.0+/-4.6 days; P < 0.05) with no difference in luteal phase length or progesterone concentrations. In GnRH agonist-treated baboons, mean (+/- SE) cycle length was prolonged to 46.3+/-1.6 days and in saline-treated controls was 32.8+/-0.8 days (P < 0.001), again this was completely represented by the change in follicular phase length, from 13.4+/-0.7 days in controls to 27.2+/-2.1 days in agonist-treated baboons (P < 0.001). In contrast, there was no significant difference in luteal phase length between these two groups (19.4+/-0.7 versus 19.2+/-1.0 days). The prolongation of the follicular phase was accompanied by significant increases in both progesterone (P < 0.01) and oestradiol (P < 0.01) during GnRH agonist treatment above control concentrations. Luteal phase concentrations of these hormones were not different from controls. These results demonstrate the previously unreported finding that gonadotropin stimulation will rescue the corpus luteum in the next follicular phase.

Atrial natriuretic peptide, oestradiol and progesterone in women undergoing spontaneous and gonadotrophin-stimulated ovulatory cycles

The objective of this study was to examine the relationship between the concentrations of oestradiol and progesterone on the one hand and atrial natriuretic peptide (ANP) concentrations on the other, during the follicular and luteal phases of spontaneous and gonadotrophin-stimulated ovulatory menstrual cycles. A total of 27 ovulatory women undergoing either a spontaneous (n = 9) or a gonadotrophin-stimulated (n = 18) cycle were selected for inclusion in this study. In comparison with spontaneous cycles, gonadotrophin-stimulated cycles had increased peak follicular oestradiol (mean +/- SE; 937 +/- 150 versus 195 +/- 18 pg/ml; P < 0.05) and midluteal progesterone (mean +/- SE; 44.0 +/- 7.4 versus 14.1 +/- 2.4 ng/ml; P < 0.05) concentrations. There were no differences in the circulating ANP concentrations between the follicular and luteal phases of the menstrual cycle. Despite the increased oestradiol and progesterone concentrations following gonadotrophin stimulation, no difference in ANP concentrations was seen between stimulated and spontaneous cycles. There was no correlation between circulating concentrations of oestradiol, progesterone (at physiological and supraphysiological concentrations) and ANP throughout the menstrual cycle.

Immunoneutralization with a monoclonal antibody attenuates the superstimulatory effects of PMSG on endocrine and ovarian responses in red deer ( [formula omitted

Superovulation has proved to be a problematic part of embryo transfer in red deer as in other domestic ruminants. Use of PMSG in red deer hinds has been associated with disturbance of follicular development and the endocrine environment. In this study, the effects of PMSG neutralization with a monoclonal antibody on the ovulation rate and the associated LH surge were investigated. Thirty mature hinds were treated during the breeding season with intravaginal progesterone impregnated CIDR devices and divided into 6 treatment groups. Group 1 received no further treatment and served as controls. All other groups were treated with 1200 IU PMSG at −72 h (CIDR withdrawal = time 0). Group 2 received no further treatment. Groups 3 through 6 received a single intravenous injection of a monoclonal antibody to PMSG at −72, 0, 12 and 24 h respectively. Blood samples were taken throughout the experiment and for a 72 h intensive sampling period following CIDR device withdrawal and analyzed for progesterone and LH, respectively. Ovarian response was assessed at laparoscopy on Day 7. The proportion of animals with more than 1 corpus luteum was higher in PMSG-only and +24 h groups than in control, −72, 0 and +12 h groups (P < 0.05). Compared with the PMSG-only treated animals, ovulation rate in PMSG-treated hinds was reduced following treatment with the antibody at −72, 0 and +12 h (P < 0.05) and the number of large Graafian follicles was reduced in all antibody-treated groups. The incidence of a LH surge was lower in the 0 and +12 h than in the PMSG-only and +24 h groups (P < 0.05). Peak progesterone concentrations in hinds treated with PMSG only and antibody at +24 h were higher than in hinds of the other treatment groups (P < 0.05). Two hinds treated with PMSG alone underwent premature luteal regression, evinced by a sharp decline in progesterone after Day 7. These results suggest that passive immunization neutralizes the biological action of PMSG in red deer, and may provide a means of overcoming some of the adverse effects of the hormone. However, the timing of the antibody treatment is crucial to ensure lack of interference with the endogenous LH surge and subsequent ovulation.

Effect of Progesterone on the Expression of Estrus at the First Postpartum Ovulation in Dairy Cattle

Fifty-two lactating Holstein cows were randomly assigned to receive either a progesterone-releasing (2g of progesterone) or a control-releasing intravaginal device (0g of progesterone). Intravaginal devices were inserted on d 10 and removed on d 15 postpartum. Daily blood samples were collected from d 10 to 90 postpartum for subsequent determination of progesterone concentrations. Observations for estrus were conducted three times daily in a dirt paddock containing a testosterone-treated cow.Serum concentrations of progesterone in the progesterone-releasing intravaginal device group were elevated on d 11, 12, 13, 14, and 15 compared with those of the control group. The days to first postpartum ovulation were similar between the treated and control groups, respectively (30.6 vs. 30.5 d). Also similar was the proportion of cows expressing estrus at first, second, and third postpartum ovulations (9/27 vs. 3/24, 14/23 vs. 15/ 21, and 14/21 vs. 9/15, respectively), length of the first postpartum estrous cycle (17.9 vs. 18.3 d), and peak serum concentrations of progesterone during the first estrous cycle (3.5 vs. 2.9ng/ml). These data indicate that administration of progesterone early postpartum did not increase the proportion of cows expressing estrus at the first ovulation.

Prolactin and progesterone concentrations during early pregnancy and relationship to pregnancy loss prior to day 45

Summary Eleven multiparous Quarter Horse and Thoroughbred mares were used to determine the plasma concentrations of progesterone and prolactin during early pregnancy and to examine the relationship of plasma progesterone and prolactin to pregnancy loss prior to d 45 of gestation. Plasma samples were collected at two day intervals beginning on d 14 of pregnancy (d 0 = ovulation) and countinued to d 80. Ovulation and pregnancy status were determined by ultrasonography. Four mares experienced pregnancy loss between d 28 and 44 and plasma samples were collected for 10 days beyond the detected loss. Seven mares had successful pregnancies (Term group). Plasma progesterone concentrations peaked by d 28 in the Term group, with individual peak values ranging from 14.9 to 31.9 ng/ml. Values then declined until d 36, followed by a rise until d 80. Prior to d 45 of gestation 5 of the 7 mares had a peak in excess of 15 ng/ml and 3 of these had brief periods, ranging fron 1 to 8 days when progesterone dropped to less than 2 ng/ml. The other 2 mares had peak plasma progesterone concentrations of less than 7 ng/ml, but maintained concentrations in excess of 2 ng/ml during this period. Within the mares experiencing pregnancy loss, 2 mares had a decline in plasma progesterone concentrations prior to pregnancy loss, while the other 2 had typical progesterone patterns beyond the detected loss. Differences in individual patterns of plasma progesterone concentration were observed in both groups (P Plasma prolactin concentrations ranged from less than .32 to 4.58 ng/ml in the Term group and from .31 to 1.9 ng/ml in the mares experiencing pregnancy loss. Differences in the individual patterns of prolactin secretion were observed in both groups (P A correlation between progesterone and prolactin was observed in the Term group between day 14 and 37 (P 2 =.88).

Attenuation of preovulatory gonadotrophin surges by epostane: a new inhibitor of 3β-hydroxysteroid dehydrogenase

Epostane, an inhibitor of 3 beta-hydroxysteroid dehydrogenase, was administered orally to pro-oestrous rats to evaluate further a possible role for preovulatory progesterone secretion in eliciting surges of LH and FSH. Whereas a dose of 10 mg epostane/kg had essentially no effects on preovulatory gonadotrophin surges and ovulation, 200 mg epostane/kg markedly attenuated LH and FSH surges and blocked ovulation. A dose of 50 mg epostane/kg exerted effects on LH and FSH surges and ovulation intermediate between those of doses of 10 and 200 mg/kg. Plasma concentrations of progesterone were significantly lower in all anovulatory epostane-treated rats at 18.00 and 22.00 h on proestrus than those measured in vehicle-treated rats. Concurrent injection of 2 mg progesterone in rats given 200 mg epostane/kg restored gonadotrophin surges to normal, but consistently failed to reverse the inhibitory effects of epostane on ovulation. Peak plasma progesterone levels produced by the progesterone injections were eight- to tenfold higher than the highest levels measured in vehicle-treated rats during the afternoon of pro-oestrus. Insertion of progesterone capsules was less effective than injections of progesterone in restoring gonadotrophin surges to normal, even though peak plasma progesterone concentrations achieved after insertion of two 20 mm long progesterone capsules were double the peak progesterone concentrations measured in control rats. Nevertheless, taken together with recent reports showing attenuation of preovulatory gonadotrophin surges by the progesterone antagonist RU 486 (17 beta-hydroxy-11 beta-[4-dimethyl-aminophenyl]-17 alpha-[prop-1-ynl] estra-4,9-diene-3-one), the present results provide support for a role of preovulatory progesterone secretion in enhancing oestrogen-dependent LH/FSH surges on pro-oestrus.

Effect of Beta-Carotene Supplementation on Reproductive Performance of Lactating Holstein Cows

Fifty-four lactating Holstein cows were assigned by parity and calving date to a 2×3 factorial arrangement of a randomized block design to determine effects of β-carotene supplementation and ration fiber content on reproduction. Because ration fiber treatments did not differ in their effects on reproductive performance, data for β-carotene analyses were pooled over the three rations. From 3 to 98 d postpartum, cows were individually fed either 0 or 300mg supplemental β-carotene daily by adding it on top of their complete mixed ration.By wk 3 postpartum, concentrations of β-carotene in blood serum were higher in cows fed supplemental β-carotene and remained higher throughout the experimental period. Feeding supplemental β-carotene had no effect on the interval from the time of parturition to uterine involution, ovulation, first observed estrus, or conception. Feeding β-carotene did not influence incidence of cystic follicles based on palpation, ovarian cyclicity based on blood progesterone patterns, peak progesterone concentrations, or first service conception rate. Cows fed supplemental β-carotene required fewer treatments for clinical mastitis. Reproductive performance in lactating Holstein cows was not improved by feeding supplemental β-carotene.

Effect of trenbolone acetate on ovarian function in culled dairy cows.

The ovarian cycles of 48 culled dairy cows were monitored by assaying plasma progesterone concentrations. Twenty-four cows received a subcutaneous implant of 300 mg trenbolone acetate (Finaplix; Hoechst) at the beginning of the study. Of the implanted cows, two were pregnant, six continued to cycle although their peak progesterone concentrations were significantly lower than in control cows (5.65 +/- 0.71 compared with 8.19 +/- 0.47 ng/ml; P less than 0.01). Prolonged periods (13 to 92 days) of low progesterone concentrations (less than 1 ng/ml) occurred in 12 of the implanted cows. In six of seven cows in which normal cycles had not resumed by the time of slaughter two to five ovarian follicles of diameter greater than or equal to 10 mm were found post mortem. Persistent luteal function (greater than 35 days) occurred in the absence of pregnancy or gross uterine pathology in five of the implanted cows, two of which had recovered spontaneously by the time they were slaughtered. There was no difference in plasma luteinising hormone concentrations between the implanted and control cows. It is concluded that trenbolone acetate affected the ovarian cycle of the cows in several ways through changes other than the modification of tonic luteinising hormone secretion.

Antifertility effect of busulfan and DL-6-(N-2-pipecolinomethyl)-5-hydroxy-indane maleate (PMHI) in coyotes ( [formula omitted][formula omitted

Antifertility effects of busulfan were evaluated using adult coyotes. In addition, antifertility effects of PMHI were evaluated in adult males. Adult males and females were alloted randomly to the following treatments: (1) untreated control, (2) a single oral dose of 3 mg busulfan/kg of body weight (BW) or (3) two oral doses of 3 mg busulfan/kg BW given nine days apart. The untreated males were used as controls in both experiments. Additional male coyotes were allotted randomly to PMHI treatments as follows: (1) a single oral dose of 2 mg PMHI/kg BW, or (2) two oral doses of 1 mg PMHI/kg BW given seven days apart. Blood samples were taken from females and serum analyzed for progesterone by radioimmunoassay. Males were hemicastrated (left testicle) 30 days after onset of treatment. The right testicle was removed 30 days later. Testes and epididymides were fixed in 10% buffered formalin and prepared for histologic examination. For females developing corpus luteum (CL), the maximum peak progesterone concentration for those given two doses of busulfan was less (P<0.05) than that for untreated controls and single-dose females (16.9, 22.4 and 26.3 ng/ml, respectively). The double treatment of busulfan prevented more females (4 of 10) from developing CL (P<0.08) than controls (0 of 7) or single-dose females (1 of 9). None of the busulfan-treated male coyotes had histologic evidence of spermatogenesis 60 days after the onset of treatment. The oral dose or doses of PMHI did not result in complete degeneration of seminiferous tubules. Busulfan given orally did not cause any adverse reactions, but orally administered PMHI often induced vomiting within 18 min after treatment. We conclude that busulfan is capable of affecting male and female reproductive parameters, but PMHI appears to have little effect on spermatogenesis in coyotes when given orally in a single- or a double-dose.

Small doses of human chorionic gonadotropin prevent estradiol-induced luteolysis.

The manner in which exogenous 17 beta-estradiol (E2) induces premature luteolysis in primates is unclear. In an effort to determine whether exogenous luteotropic hormone inhibits E2-induced luteolysis, E2 capsules were implanted subcutaneously in 11 cynomolgus macaques during the early luteal phase; six animals received injections of human chorionic gonadotropin (hCG; 7.5, 10, or 15 IU/day) for 10 days, and the remaining monkeys received saline. Blood was collected once daily for measurement of E2, progesterone, and bioactive luteinizing hormone (LH). Peak progesterone concentrations were between 0.7 and 5.0 ng/ml and declined prematurely in monkeys given E2 plus saline; the luteal phase was 11.5 +/- 0.6 days (mean +/- SE). With E2 plus hCG treatment, serum progesterone continued to increase after E2 capsule placement and reached peak levels of 4.0-13.0 ng/ml; the luteal phase was 15.3 +/- 0.5 days. Therefore, E2-induced luteolysis was overcome by concurrent administration of hCG. These results suggest that exogenous tropic hormone circumvents the inhibitory influence of E2 on luteal function, but the details of the interaction remain unknown.

Luteal competency during the resumption of ovarian cyclicity in postpartum Brahman cows

Twenty pluriparous, spring-calving Brahman cows were used to determine luteal competency, as measured by serum progesterone concentrations, during the first and the second postpartum estrous cycles. Prior to and after calving, all cows were maintained in good body condition on Coastal bermudagrass pasture (IFN 1-00-703). The calves were allowed to suckle ad libitum, and sterile marker bulls were maintained with the cow herd as an aid in estrus detection throughout the trial. Cow weight and body condition score were recorded within 24 hours after calving and again at the first behavioral estrus observed. From day 1 through day 14 (day 0 = estrus) of both the first and the second postpartum estrous cycles, blood samples were collected from each cow, processed to yield serum and analyzed by radioimmunoassay for progesterone concentrations. There was a higher incidence of abnormal estrous cycles following the first postpartum estrus (35%) than following the second (5%) postpartum estrus (P<0.05). The abnormal first estrous cycles were characterized by either a short luteal phase (four cows) or by standing estrus behavior without luteal tissue formation (three cows). When serum progesterone concentrations were compared for all cows during the first estrous cycle with those during the second estrous cycle, there was less progesterone released during the cycle (P<0.05) and lower peak progesterone concentrations (P<0.10) during the first estrous cycle. However, if the abnormal cows were excluded from the analyses, there was no difference (P>0.10) in either progesterone concentrations through the 14 days measured or in peak progesterone concentrations between the first and the second postpartum estrous cycles. It can be concluded from this study that the higher incidence of abnormal luteal function following the first postpartum estrus may contribute to the decreased conception rates observed when cows are bred at their first postpartum estrus.

Progesterone, fluid, and electrolytes in premenstrual syndrome.

Changes in mood, plasma progesterone concentration, urinary volume, sodium excretion, sodium:potassium ratio, and body weight during the menstrual cycle were determined in 18 women with premenstrual syndrome and 10 symptomless (control group) women. Plasma progesterone concentration was higher in the women with symptoms during the postovulatory phase of the cycle, and the peak progesterone concentration appeared earlier. The changes in progesterone concentration were accompanied by a natriuresis and diuresis that fell towards preovulatory values in the premenstrual phase. Sodium retention was not confined to any definite period. Mood symptoms occurred after the changes in progesterone and electrolyte concentrations. Progesterone deficiency is probably not the cause of premenstrual syndrome. Thus treatment with progesterone is probably illogical unless a deficiency is detected. Treatment should be aimed at preventing the natriuretic effect of progesterone in the postovulatory phase and the sodium-retaining and water-retaining effects of aldosterone in the premenstrual phase.

Effect of presence of the male on initiation of estrous cycle activity of goats

Serum progesterone concentrations and behavioral estrus were determined in two groups of 17 mixed breed dairy does at the beginning of the breeding season. The treatment group was pastured adjacent to two mature bucks while two teaser bucks ran with the group. The control group was pastured without exposure to bucks. Goats were observed for estrus daily for 35 days and samples of jugular blood were collected every other day for radioimmunoassay of progesterone. Signs of estrus were observed in 16 of 17 does in the treatment group within a mean ± S.E. of 5.5 ± 1.3 days after introduction of the bucks. Thirteen does demonstrated a progesterone profile characteristic of a normal estrous cycle with peak progesterone concentrations of 5.9 ± 0.5 ng/ml. Signs of behavioral estrus were not observed in the control group. One control doe demonstrated a progesterone profile characteristic of a normal estrous cycle attaining a peak progesterone concentration of 3.9 ng/ml. Progesterone concentrations in the remaining 16 control does were at or near the lower limits of sensitivity of the assay for the duration of the experiment. Fifteen of the control does exhibited estrus within 7 ± 1.5 days after exposure to bucks at the end of the experiment. These results clearly demonstrated a profound influence of the male on estrous cycle activity during the beginning of the breeding season.

Steroids in pregnancy and parturition in the marsupial, Macropus eugenii

Pregnancy in the tammar wallaby, Macropus eugenii may be prolonged by a long period of embryonic diapause of the 100-cell blastocyst; resumption of development occurs after removal of the suckling pouch young (RPY) or by exogenous progesterone injection. The corpus luteum is essential for the first 8 days of pregnancy, but is not required for normal development after this time. Normal parturition will only occur, however, if the corpus luteum is present up to at least day 21 of pregnancy. The corpus luteum produces and contains progesterone, but peripheral plasma values are low (1 ng/ml). The peak progesterone content in the corpus luteum is attained at day 23 RPY, and is followed by a peak plasma concentration at day 25. Levels in both fall markedly by the day of birth, day 27 RPY. Ovariectomy will abolish the peak progesterone concentration in the peripheral plasma. Contractile activity of the myometrium is inhibited throughout gestation, probably by progesterone, since exogenous progesterone delays parturition. The pregnant uterus shows less electrical activity than the contralateral uterus, but is more responsive to oxytocin. This implies the existence of local regulatory mechanisms within the pregnant uterus. Fetal cortisol production may be involved in the initiation of parturition, and progesterone withdrawal appears to be necessary for birth. These data are summarised into an hypothetical scheme showing possible control mechanisms for parturition in the tammar wallaby.

Plasma Concentration of Progesterone and Estradiol during the Ovulatory Cycle of the Turkey

Radioimmunoassays were used to estimate concentrations of progesterone and estradiol in the peripheral plasma of hens in relation to the first (C1) or second (C2) ovulation in a sequence. Peak concentrations of progesterone were found at 6–3 hr. before ovulation.There were no consistent changes in estradiol concentrations. When blood samples were taken at 2-hr. intervals for 24–28 hrs., estradiol concentrations peaked at 18 hours before C1 ovulation and during the same time of day (2–6 p.m.) during die period of no ovulation between sequences, but no estradiol peak preceded C2 ovulation. When blood samples were taken from a second population of hens at 1-hr. intervals during the 12 hr. period before expected C2 ovulation, a significant rise in estradiol (P<0.01) was associated with the preovulatory peak of progesterone. The preovulatory peak of estradiol in these hens may be linked to a seasonally high rate of secretion of both estradiol and progesterone. As estimated indirectly by hypophysectomy, release of an ovulatory amount of LH in the turkey coincided with the rise of progesterone to the preovulatory peak.

Progesterone and 5alpha-pregnane-3,20-dione in peripheral blood of normal young women: Daily measurements throughout the menstrual cycle.

The peripheral plasma concentrations of progesterone and 5alpha-pregnane-3,20-dione were measured daily throughout the ovarian cycle of five presumptively ovulatory women. The concentrations of progesterone and 5alpha-pregnane-3,20-dione during the follicular phase were 0.11 +/- 0.02 ng/ml (mean +/- SE) and 0.16 +/- 0.01 ng/ml, respectively. In four of these women the concentrations of both progesterone and 5alpha-pregnane-3,20-dione began to rise immediately after the luteinizing hormone (LH) peak and reached maximal concentrations five to eight days later (progesterone: 8.6 to 19.9 ng/ml; 5alpha-pregnane-3,20-dione: 1.4 to 2.8 ng/ml). The luteal phases in these women, measured from the day of the LH peak to the onset of the next menses, varied from 13 to 18 days. In the other woman with a late LH surge (day 27 of the cycle) the peak concentrations of progesterone and 5alpha-pregnane-3,20-dione were reached four days after the LH peak (8.9 ng/ml and 0.8 ng/ml, respectively). The luteal phase in this woman was 11 days. From the results of this study, it appears that the concentrations of 5alpha-pregnane-3,20-dione in peripheral blood during the luteal phase are proportional to the availability of progesterone as substrate for the 5alpha-reductase enzyme system.

Ovarian progesterone levels during in vitro oocyte maturation and ovulation in Xenopus laevis.

Endogenous progesterone was measured in ovaries of the frog Xenopus laevis following the administration of gonadotropins that induce meiotic maturation and ovulation of large oocytes. Ovarian pieces were incubated for 0, 1, 3, 5, or 10 h in Gurdon’s solution in the presence or absence of human chorionic gonadotropin (HCG; 20 lU/mI) or a frog pituitary homogenate (FPH; 0.04 pituitary/mI). Each incubation sample was scored for ovulation and maturation at the end of its incubation period, homogenized in the medium, and extracted for progesterone with petroleum ether. Following purification on Sephadex LH-20, extracts were assayed for progesterone by a radioimmunoassay that was validated for use with frog ovarian tissue. In 13 experiments, mean (! SEM) progesterone concentration in untreated ovarian tissue was 3.7 ± 0.5 ng/gm at time zero and progesterone levels did not change significantly during 10 h of incubation. HCG-treated tissue (n = 6) exhibited a linear, two-fold increase in progesterone for the first 3 h of incubation and maintained that level for the remainder of the incubation. FPH treatment (n = 10) produced a linear six-fold increase in progesterone over the course of 10 h. Mean progesterone content across time was significantly greater (P<0.005) in FPH-treated tissue than in HCG-treated tissue. Both differed significantly (P<0.05) from untreated controls. In tissue treated with HCG the percent oocyte maturation was correlated (P<0.10) with both mean progesterone concentration across time and progesterone concentration at 10 h of incubation; ovulation did not occur. In FPH-treated tissue progesterone concentration was not correlated with percent maturation but was correlated (P<0.05) with the number of ovulations/gm. Treatment of ovarian pieces with the gonadotropins following a 10 h incubation in Gurdon’s solution produced effects similar to those following treatment at time zero. In vivo treatment with HCG prior to in vitro incubation of ovarian tissue with HCG or FPH resulted in an eight- or eleven-fold increase, respectively, in peak progesterone concentration as compared to tissue that was not pretreated in vivo. In two experiments large, preovulatory follicles contained sufficiently more (P<0.05) progesterone following FPH treatment than did smaller follicles. Both large and small FPH-treated follicles had significantly higher levels of progesterone than untreated control tissue.