Changes In Plasma Luteinizing Hormone Research Articles

Plasma levels of luteinizing hormone and prolactin in relation to double brooding in Great Tit (Parus major)

The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis. Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages. However, only a few studies have examined the temporal trend of hormone levels among different reproductive stages in multiple brooded species. We investigated the changes in plasma luteinizing hormone (LH) and prolactin (PRL) concentrations during different reproductive stages of the facultative double-brooded Great Tit (Parus major). We found that the concentrations of LH and PRL in females were significantly higher than those in males. Females had significantly higher LH and lower PRL concentrations in the pre-breeding period than in the first/second brooding periods, and there were no significant changes between the first and second brooding periods. The concentrations of LH and PRL in males had no significant difference between the pre-breeding period and the first brooding periods, while LH and PRL concentrations in the second brooding period were significantly higher than those in the first brooding period. We conclude that there are sex-based differences between LH and PRL at different stages of reproduction. The changes in LH and PRL in both males and females should be related to their physiological functions. Especially for males, individuals with higher levels of LH and PRL are more likely to maintain second clutches.

Features of follicle-stimulating hormone–stimulated follicles in a sheep model: keys to elucidate embryo failure in assisted reproductive technique cycles

To evaluate the individual functionality of gonadotropin-stimulated preovulatory follicles, for understanding embryo failure in assisted reproductive technique cycles, in a sheep model. Observational, model study. Public research unit. Fifteen adult Manchega ewes. Synchronization of the estrous cycle with intravaginal progestagens and ovarian stimulation with FSH; evaluation of reproductive activity, plasma sampling, ovarian ultrasonography, and ovariectomies. Determination of estrus behavior, plasma and intrafollicular concentrations of E(2) and inhibin A, number and size of ovarian follicles, and developmental competence of oocytes. These results support the usefulness of serial measurements of plasma inhibin A for assessment of follicular growth during the FSH treatment, rather than of E(2) assays commonly used. Functionality of FSH-stimulated preovulatory follicles is clearly disturbed, as confirmed by a negative correlation between follicular size and intrafollicular concentrations of inhibin A and E(2) in preovulatory follicles after individual dissection; moreover, the ability of their oocytes to resume meiosis was diminished. Functionality of follicles in controlled ovarian stimulation (COS), and developmental competence of their oocytes, is disturbed by the high doses of gonadotropin supplied and finally determined by follicular sizes at starting FSH treatment.

The relation between ultrasonographic observations in the oviduct and plasma progesterone, luteinizing hormone and estradiol during the egg laying cycle in ostriches

In this study we investigated the temporal relationship between ovulation, egg formation, oviposition and the changes in plasma concentrations of progesterone, luteinizing hormone and estradiol-17β during the egg laying cycle in farmed ostriches. In 10 egg-producing birds, transcutaneous ultrasound scanning was performed at 3 h intervals and blood sampling at hourly intervals during a period of at least 48 h (one egg laying cycle). In hens ( n = 8) that ovulated during the observational period, the ovulated egg was first detected 2 h after oviposition; thus, ovulation occurred shortly after oviposition in all birds. During the period between two consecutive ovipositions, the developing egg remained for 9 h in the proximal part (infundibulum, magnum or isthmus) and for 39 h in the distal part of the oviduct (uterus). In ovulating hens, plasma progesterone concentrations showed a characteristic and consistent profile: from basal levels of around 0.1 ng/ml concentrations started to increase 12 h before oviposition, reached an average maximum of 3.5 ng/ml at 3 h before oviposition and returned to basal levels 3 h and 30 min after oviposition. Changes in plasma luteinizing hormone and estradiol-17β concentrations showed comparable patterns of elevation and decline relative to the timing of oviposition and ovulation. However, variation in their individual basal concentrations was generally larger and peak values were less conspicuous than those of progesterone. In non-ovulating hens ( n = 2) neither progesterone, nor luteinizing hormone nor estradiol-17β showed elevations to peak concentrations before oviposition. These data demonstrate that during the egg laying cycle of ostriches, events such as ovulation, egg development and oviposition evolve according to a rather strict time schedule, and that progesterone, luteinizing hormone and estradiol-17β reach peak concentrations shortly before ovulation. Additionally, our findings also show that on-farm ultrasound scanning is a useful technique to discriminate between ovulating and non-ovulating hens.

Developmental changes of plasma inhibin, gonadotropins, steroid hormones, and thyroid hormones in male and female Shao ducks

Plasma samples from developing male and female Shao ducks were assayed for immunoreactive (ir-) inhibin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), steroid hormones, and thyroid hormones. In the male, plasma ir-inhibin significantly increased between 75 and 155 days posthatch, and then decreased slightly at day 165. Plasma FSH of male ducks decreased from day 35 to day 55, followed by progressive elevation until day 95. Plasma FSH of male ducks fell significantly at days 135 and 165, while plasma ir-inhibin rose to high level. In female ducks, plasma ir-inhibin remained low until the start of lay, and thereafter significantly increased at day 135. Plasma FSH fluctuated before day 95 and significantly rose at day 115, and decreased thereafter. In males, plasma LH did not vary significantly before day 135, however, plasma testosterone significantly increased from day 95 onwards. No changes in plasma LH were observed during development of female ducks. Plasma estradiol-17β gradually increased reaching a peak level at day 135. Plasma progesterone did not vary significantly before day 135 and thereafter significantly increased. Both sexes showed a similar pattern in changes of plasma thyroid hormones during sexual development. There was a significant increase in plasma thyroxine (T 4) at day 95, thereafter decreased. Plasma triiodothyronine (T 3) was at high level at the earlier stage of development and significantly decreased at day 55. Significant increase in plasma T 3 in male and female ducks was observed at 135 and 115 days, respectively. In conclusion, these results demonstrated that the rise in inhibin is correlated with age of sexual maturity in the female while the rise in inhibin significantly precedes sexual maturity in the male. There was a progressive increase in plasma steroid hormones towards sexual maturity, and there was no sex difference in the time course of thyroid hormones.

Effects of environmental lighting on early semen production and correlated hormonal responses in turkeys

Recent work at our institution on lighting turkey males for semen production and correlated changes in plasma luteinizing hormone (LH) and testosterone (T) are summarized in this paper. In sexually mature males, both LH and T are secreted in pulses, with a pulse of LH about 10 min prior to a pulse of T. Pulses of LH and T occurred about every 2 h and were equally distributed between the light (L) and dark (D) portions of a 14 h L:10 h D d. The pattern of secretion and overall concentrations of LH and T were not affected by intermittent photoperiod lighting (1 L:2 D, 8 x d) in comparison to continuous photoperiod lighting (14 L:10 D) lighting. Pulses of LH or T were not entrained by L or D with the intermittent or continuous lighting treatment. To study the interaction of age and lighting treatment, males were exposed to one of two lighting treatments: long-day photoperiods (16 L:8 D) d(-1) from 10 to 12 or 29 wk of age (WOA) (Treatment LDLD) or short-day photoperiods (6 L:18 D d(-1) from 10 or 12 to 29 WOA, then long-day photoperiods (Treatment SDLD). Males in the LDLD treatment attained puberty earlier (25 WOA) than those in the SDLD treatment. In the later treatment, most of the males attained puberty after 29 WOA. Both LH and T were low until 18 WOA in the LDLD males, then both increased to adult levels over the next 2 to 3 wk. In the SDLD males, LH and T were lower than in the LDLD males until 48 h after switching to long-day photoperiods, when both were transiently higher before declining to lower adult levels by 35 WOA. Secretory patterns of LH and T were estimated at 13, 23, and 35 WOA, under both lighting treatments. At 13 WOA, LH and T were secreted in pulses, but levels of both hormones were low and not different between lighting treatments, and none of the birds (0/4) in either treatment were producing semen. At 23 WOA, LH and T were secreted in robust pulses, with the LDLD males having higher concentrations of LH and T than the SDLD males. At 23 WOA, most of the males in the LDLD group (3/4) but none in the SDLD group (0/4) were producing semen. At 35 WOA, 6 wk after photostimulation of the SDLD group, all males (4/4) in both groups were producing semen, and LH and T were at adult levels. However, fewer pulses of T were noted for males in the SDLD treatment.

Ontogeny of luteinizing hormone and estradiol secretion in turkey hens exposed to different photoperiods from hatch to sixty weeks of age

Changes in concentrations of plasma luteinizing hormone (LH) and estradiol-17beta in turkey hens were measured during development utilizing stimulatory and nonstimulatory lighting treatments. All hens were maintained under 24 h light (L) from hatch to 3 wk of age, then 16L:8 dark (D) to 10 wk of age. From 10 wk of age, three lighting treatments were used: 1) 16L:8D from 10 to 60 wk of age (Treatment LD); 2) 6L:18D from 10 to 60 wk of age (Treatment SD); and 3) 16L:8D from 10 to 20 wk of age, 6L:18D from 20 to 30 wk of age, and then 16L:8D from 30 to 60 wk of age (Treatment SD-LD). Measurements of plasma LH and estradiol-17beta concentrations were based on weekly blood samples. Similar patterns of LH were observed in all treatments before 24 wk of age. The concentrations of LH were high at hatch then declined to low levels at 10 wk of age and rebounded to high levels at 18 wk of age before declining to low levels at about 24 wk of age. Low concentrations of LH were then maintained for hens on all treatments but were slightly higher in hens on Treatment SD from 35 to 60 wk of age. A transitory increase in LH, lasting about 3 wk, occurred for hens on Treatment SD-LD after photostimulation. The concentrations of estradiol-17beta were low and stable for hens on all treatments when they were not laying but were elevated about 2 wk prior to and during egg laying. All hens on Treatments LD and SD-LD laid eggs; no hens on Treatment SD laid eggs to 60 wk of age. It was concluded that 1) changes in plasma LH and estradiol-17beta were age related before about 24 wk of age, 2) turkey hens may not be photorefractory at hatch and can lay without juvenile exposure to SD photoperiods, and 3) LD photoperiods after about 20 wk of age are necessary for initiation of egg production in turkey hens before 60 wk of age.

Effect of age and body weight on plasma concentrations of luteinizing hormone in turkey hens before and after photostimulation

The independent effects of age and body weight (BW) on photostimulatory response in turkey breeder hens were studied by measuring changes in plasma luteinizing hormone (LH; ng/mL) before and 3 d after photostimulation. The study was conducted with hens from two BW groups at 24–25, 27–28, and 31–32 wk of age. There was approximately a 1-kg difference in BW between groups within an age. Six hens per BW and age group were cannulated (jugular vein) and serially sampled during each of two 6-hr periods. Samples were collected at 10-min intervals. The two sampling periods were the last 6 hr of the short-day photoperiod (SD) and the same period during the third long day after photostimulation (LD). The photostimulatory response (PR) or difference between the SD and LD baseline LH concentrations was greatest in the 24–25-wk-old hens. The PR was unaffected by hen BW at any age. The baseline LH concentration during the SD photoperiod declined as hens aged. After photostimulation, baseline LH and LH peak amplitude concentrations were higher in 24–25-wk-old hens compared with the older ages. The number of LH peaks increased after photostimulation, but there were no significant effects attributable to age or BW within an age. In conclusion, the PR was affected by hen age but not hen BW or BW within a particular age.

Changes in plasma luteinizing hormone, testosterone and estradiol-17 beta levels and semen quality after injections of gonadotropin releasing hormone agonist and human chorionic gonadotropin in three dogs with oligozoospermia and two dogs with azoospermia.

Plasma luteinizing hormone (LH) and testosterone (T) levels in three normal male Beagles increased markedly, the LH levels peaking at 30 or 45 min and the T levels at 45 or 60 min respectively, after a subcutaneous injection of 1 microgram kg-1 gonadotropin releasing hormone agonist (GnRH-A). Two Collies and a Great dane diagnosed as oligozoospermic and two Shetland sheep dogs diagnosed as azoospermic by evaluation of semen quality were treated with 1 microgram kg-1 GnRH-A after blood collection. Their plasma levels of LH, T and estradiol-17 beta (E2) were measured by radioimmunoassay for the purpose of investigating the effect of hormone therapy on spermatogenic dysfunction and the mechanism on improvement of semen quality. The semen quality of one of the Collies had improved 4 weeks after the GnRH-A treatment. The dog was treated with GnRH-A again and mated with a bitch 4 days later. The bitch gave birth to five puppies. The other dogs, whose semen quality had not improved, were treated with an intramuscular injection of 500 or 1000 IU human chorionic gonadotrphin (hCG) per animal. Since the semen quality of the other Collie and the Great Dane improved temporarily 2 and 4 weeks, respectively, after hCG treatment, the former was mated with a bitch 5 days later. The bitch gave birth to a litter of seven puppies. These hormone treatments, however, had no effect on the azoospermia in the two Shetland sheep dogs. Although the mean plasma LH and T levels in the dogs with oligozoospermia had been low, their LH levels gradually increased after hormone treatment. There were no marked changes in plasma T or E2 levels. These findings indicate that the semen quality of dogs with oligozoospermia can be temporarily improved between 2 and 4 weeks after a single injection of GnRH-A or hCG and the fertility of the dogs restored by the injection.

A Rapid Suppressive Effect of Estrogen in the Paraventricular Nucleus on Pulsatile LH Release in Fasting‐Ovariectomized Rats

The paraventricular nucleus (PVN) and A2 are novel estrogen feedback sites where estrogen may modulate the neural response to adrenergic inputs during fasting. In the present study, the effects of local estradiol (E(2)) perfusion through a microdialysis probe placed in the PVN or A2 on pulsatile luteinizing hormone (LH) secretion and on norepinephrine (NE) release in the PVN were examined in 48-h fasting ovariectomized (OVX) rats to determine whether local estrogen administered in the PVN or A2 rapidly inhibits LH secretion during fasting and whether this inhibition is mediated by an increase of NE release in the PVN. Five days after ovariectomy, animals (n=5 per group) stereotaxically implanted with a guide cannula for microdialysis in the PVN (experiment 1) or both PVN and A2 (experiment 2) were deprived of food for 48 h. Blood samples and dialysates were then collected every 6 min for 3 h and every 12 min (experiment 1) or 20 min (experiment 2) for 3 h, respectively. The PVN or A2 was perfused with E(2) (5 ng/ml in artificial cerebrospinal fluid) through a microdialysis probe after the first hour of sampling. E(2) perfusion in the PVN caused a rapid and significant suppression of mean plasma LH levels and LH pulse frequency in fasting rats but no changes in unfasting animals. NE release in the PVN was not affected by the local E(2) perfusion of the PVN in either fasting or unfasting groups. This perfusion in A2, however, did not cause any apparent changes in plasma LH and perfusate NE levels in the PVN and A2. The present results indicate that estrogen feedback action at the PVN suppresses LH secretion rapidly during fasting and does not involve an increase of NE release in the PVN.

Effect of Reproductive Condition on Luteinizing Hormone and Prolactin Release Induced by Electrical Stimulation of the Turkey Hypothalamus

In the turkey, the onset or incubation behavior is associated with decreased luteinizing hormone (LH) and increased prolactin (PRL). This study was designed to clarify the contribution of the hypothalamus and the anterior pituitary to the changes in plasma LH during the reproductive cycle of the turkey. Plasma LH and PRL were measured in anesthetized turkey before, during, and after electrical stimulation in the median eminence. In one experiment, luteinizing hormone releasing hormone (LHRH; 4 μg/kg) was injected intramuscularly 30 min after termination of electrical stimulation, and blood samples were obtained 5, 10, 20, and 30 min after injection. Electrical stimulation in the median eminence significantly increased (P < 0.05) plasma LH of laying (LAY), nest-deprived, previously incubating (NEST DEP), and photorefractory (REFRAC) hens, but not of photosensitive short-day (SHORT DAY) birds (P > 0.05). Plasma LH of LAY hens peaked at 4.06 ± 0.78 ng/ml from a prestimulation baseline or 2.30 ± 0.21 ng/ml and that in NEST DEP birds increased from 1.08 ± 0.18 ng/ml to 2.57 ± 0.53 ng/ml. Administration of LHRH increased plasma LH levels in SHORT DAY, LAY, and NEST DEP hens with the increase being 2.0-. 2.5-, and 6.1-fold, respectively. Electrical stimulation in the median eminence increased plasma PRL (P < 0.05) in all the reproductive groups tested, with peak response being greatest for NEST DEP birds (661 ± 126 ng/ml followed by LAY (317 ± 26 ng/ml). REFRAC (50 ± 7 ng/ml. and SHORT DAY (39 ± 12 ng/ml) hens. These results are interpreted to indicate that the reduced plasma LH levels in NEST DEP hens appear to be due to functional limitations of central neural mechanisms afferent to the median eminence and not to the inability of either median eminence or anterior pituitary to respond.

Effects of tamoxifen on endometrial estrogen and progesterone receptor concentrations in women with fibrocystic disease of the breast.

Endocrine changes were determined after a 3-week cycle of tamoxifen treatment in 11 regularly cycling women with clinical and radiological evidence of fibrocystic disease of the breast. Blood and endometrial samples were obtained during the luteal phase prior to and at the end of treatment. Tamoxifen treatment (20 mg/day orally for 3 weeks), produced a significant increase in plasma estradiol (p = 0.0018) without simultaneous changes in plasma luteinizing hormone, follicle stimulating hormone, prolactin or progesterone. Tamoxifen treatment significantly reduced endometrial estrogen receptor levels compared to the control cycle (p = 0.0018) while endometrial progesterone receptor levels remained unchanged. Endometrial histological studies showed secretory transformation in both the control cycle and after tamoxifen treatment. The reduction in endometrial estrogen receptor concentrations would suggest a tamoxifen-induced effect or a down-regulatory mechanism to protect target tissues from high estradiol levels. These changes were not associated with alterations in either plasma progesterone or endometrial progesterone receptor concentrations. The tamoxifen-induced changes did not produce any interference in the glandular secretory response of the endometrium.

Reproductive endocrinology of macaroni ( Eudyptes chrysolophus) and gentoo ( Pygoscelis papua) penguins : I. Seasonal changes in plasma levels of gonadal steroids and LH in breeding adults

Changes in plasma luteinizing hormone (LH), testosterone, oestradiol, and progesterone were measured throughout the breeding and molt cycle in free-living male and female macaroni ( Eudyptes chrysolophus) and gentoo ( Pygoscelis papua) penguins, at Bird Island, South Georgia (54°S, 38°W). These two species are sympatric but have a markedly different breeding cycle. In macaroni penguins plasma levels of all hormones, except LH in males, were significantly elevated at the time of arrival at the breeding colony. In both species and sexes plasma LH, testosterone (males), and estradiol (females) levels were highest during nest-building and postcopulation, coincident with the period of frequent agonistic interactions in males and egg-formation in females. Elevated testosterone levels occurred in females of both species during the postcopulation period and may be associated behaviourally with both sexes being involved in nest defence. Male birds also had elevated estradiol levels. Following copulation, plasma levels of LH, testosterone, and estradiol decreased to basal levels in both sexes and species and, except for a transient increase in testosterone in male macaroni penguins, remained low through to the end of molt. There was no associated rise in LH or testosterone during premolt and early molt despite a further period of agonistic and social interaction, suggesting that birds were in a photorefractory state at this time. Plasma progesterone showed a pattern of variation different from that of the other hormones. In both species and sexes, plasma levels were elevated between arrival and early chick-rearing and then decreased slowly to low levels during molt.

Medial Preoptic Microimplants of the Antiestrogen, Keoxifene, Affect Luteinizing Hormone‐Releasing Hormone mRNA Levels, Median Eminence Luteinizing Hormone‐Releasing Hormone Concentrations and Luteinizing Hormone Release in Ovariectomized, Estrogen‐Treated Rats

Abstract We examined the temporal changes in plasma luteinizing hormone (LH) levels, median eminence luteinizing hormone-releasing hormone (LHRH) concentrations and LHRH mRNA levels in estrogen-treated, ovariectomized rats with empty or antiestrogen- containing microcannulae stereotaxically implanted into the medial preoptic area. Neither treatment disrupted the negative feedback effects of estrogen on LH secretion, but antiestrogen (Keoxifene) blocked the afternoon LH surges. In rats exhibiting LH surges, median eminence LHRH concentrations were similar at 0800, 1200 and 1600 h, but they were significantly elevated by 2000 h. In contrast, no alterations in LHRH concentrations occurred in the Keoxifene-treated group. LHRH mRNA levels in control rats were significantly elevated at 1200, 1600 and 2000 h compared with 0800 h, but LHRH mRNA levels in Keoxifene-treated rats did not change significantly over the time period examined. When we compared treatment effects over time we saw that serum LH levels were significantly higher in control than Keoxifene-treated rats only at 1600 and 2000 h. Median eminence LHRH concentrations did not differ between treatment groups until 2000 h when control animals had significantly higher levels than those of Keoxifene-treated animals. LHRH mRNA levels in Keoxifene-treated rats were significantly higher than those of controls at 0800 hand significantly lower at 1600 h. No differences in LHRH mRNA levels were detected between groups at either 1200 h or 2000 h. In summary, although it was not clear on which neuronal system estrogen acted, depriving medial preoptic neurons of this steroid in systemically estrogenized rats certainly disrupted the neural mechanisms involved in surge, but not basal LH release. In addition, neither LHRH mRNA levels nor median eminence LHRH concentrations showed variations within the period studied when the estrogen-sensitive mechanisms involved in LH release were disrupted. Therefore, the changes in LHRH mRNA levels and LHRH concentrations in the median eminence seen in surging animals probably resulted from the same neural events which triggered LH release.

An analysis of serotonin secretion in hypothalamic regions based on 5-hydroxytryptophan accumulation or push-pull perfusion. Effects of mesencephalic raphe or locus coeruleus stimulation and correlated changes in plasma luteinizing hormone

This study evaluates the effect of electrical stimulation (ES) of the dorsal (DRN) and median raphe (MRN) nuclei serotoninergic systems on luteinizing hormone (LH) release in estrogen-treated, ovariectomized rats. To show that ES increased serotonin (5-hydroxytryptamine; 5-HT) secretion into hypothalamic regions known to contain luteinizing hormone-releasing hormone (LH- RH) cell bodies and terminals, 5-hydroxytryptophan (5-HTP) accumulation was measured in microdissected hypothalamic areas after blockade of aromatic- l-amino-acid decar☐ylase with NSD-1015. DRN-ES produced a significant increase in 5-HTP accumulation in the medial preoptic (MPN) and paraventricular nuclei (PVN), but not in the suprachiasmatic nucleus (SCN), arcuate nucleus (ARC) or median eminence (ME). In contrast, MRN-ES produced a significant rise in 5-HTP accumulation only in the PVN and ARC, not in the SCN, MPN or ME. Because the DRN receives noradrenergic innervation from the locus coeruleus (LC) we also evaluated the effect of LC stimulation on 5-HT secretion into these hypothalamic regions. LC stimulation, like DRN-ES, resulted in increases in 5-HTP accumulation in MPN and PVN, but not in SCN or ME. In addition, using push-pull perfusion methodology, we observed that LC-ES results in a 240% increase in 5-HT and a decrease of approximately 40% in 5-hydroxyindoleacetic acid (5-HIAA) in MPN perfusates collected 10–20 min after LC-ES began. With evidence that DRN- and MRN-ES evoke 5-HT release, we next examined whether such stimulation affects basal LH release. Because we were unable to find any effect, we determined whether 5-HT release would augment or suppress electrochemically evoked LH release. MPN electrochemical stimulation (ECS) induced a significant increase in plasma LH with a peak seen at 45 min. When the MPN was ECS and 30 min later the DRN was ES for 30 min no augmenting or suppressive effect was seen during the first 60 min. However, while plasma LH declined towards baseline in the MPN-ECS group, it remained significantly elevated in MPN-ECS + DRN-ES rats. MPN-ES + MRN-ES had no such effect; instead, LH levels were transiently decreased 45 min after beginning MPN-ECS. This study provides additional information on hypothalamic sites which receive axonal projections from the DRN and MRN and clearly indicate that an increase in 5-HT secretion occurs in the MPN following DRN- or LC-ES. In addition, results of this study demonstrate that activity in the noradrenergic system stimulates activity in the DRN serotonergic system, and that these systems may interact to affect LH-RH release.

Male stimulation of luteinizing hormone surge, progesterone secretion and ovulation in spontaneously persistent-estrous, aging rats.

In aging, persistently estrous (PE) female rats, there are no estrous cycles or cyclic increases in luteinizing hormone (LH) secretion, but the sexual receptivity to the male is consistently maintained. We recently reported that caging and mating with fertile males elicits an LH surge followed by ovulation in aging PE rats. The present study examined the relationship between the LH surge, the increase in progesterone (P) secretion and ovulation in PE females exposed to males, and assessed whether intromission was essential for the male-induced pre-ovulatory LH surge. PE rats were implanted with intra-atrial cannulae. Six to eight days later, these females were individually caged with a fertile male and repeatedly sampled (once every 30 or 60 min) between 1400 and 1900 h for assays of plasma LH and P. Sexual behavior of the female was recorded and correlated with the changes in plasma LH and P values. Similar experiments were also performed on cannulated PE rats with their vaginal orifice blocked with adhesive tape during the caging and sampling session. In both experiments, over 90% of the PE females displayed a high degree of lordosis response to mounting by the male, and over 60% of those sexually receptive PE females exhibited an LH surge followed by ovulation. The male-induced preovulatory LH surge occurred in PE females without actual intromission. Caging with fertile males also elicited a marked increase in plasma P concentrations in PE rats and in PE females prevented from experiencing intromission.(ABSTRACT TRUNCATED AT 250 WORDS)

The release of pituitary LH and sprouting of LH-releasing hormone (LHRH)-containing neurons after anterior hypothalamic deafferentation

The chronology of changes in plasma luteinizing hormone (LH) and the distribution of immunoreactive neuronal processes containing LH releasing hormone (LHRH-ir) were studied in the female rat after surgical interruption of anterior neural connections of the mediobasal hypothalamus (MBH). Spontaneous LH surges on the afternoon of proestrus and LH release of proestrus and LH release after estradiol benzoate (EB) followed 48 h later by progesterone (P) administration were studied in ovariectomized (OVX) rats. The maximum increase in plasma concentrations (Δ maxLH) after EBP was calculated for each rat at several intervals over 140 days. Control animals given EBP at monthly intervals after OVX had comparably largeΔ maxLH surges during the first few months of study. However, a gradual decline in controlΔ maxLH followed becoming significant 3 months after the start of the experiment. In contrast, frontal cuts (FC), which interrupted anterior MBH connections, produced an abrupt decrease inΔ maxLH surges after EBP to 11% of preoperative levels. However, during subsequent EBP trials, there was a gradual improvement in LH surges to about 50% of preoperative levels over 100 days. In some cases, individual improvement became equal to preoperative LH surge levels, in others there was no recovery. Examination of LHRH-ir nerve growth responses after FC suggested that sprouting by these peptide-containing neuronal process may have contributed to the functional improvements observed.

Endocrine changes in photostimulated willow ptarmigan ( Lagopus lagopus lagopus) and Svalbard ptarmigan ( Lagopus mutus hyperboreus)

Changes in plasma luteinizing hormone (LH), testosterone, thyroxine (T 4), and triiodothyronine (T 3) and the height of supraorbital combs were compared in captive willow ptarmigan ( Lagopus lagopus lagopus) and Svalbard ptarmigan ( Lagopus mutus hyperboreus) exposed to an artificial annual cycle of daylength simulating that at 70°N. Plasma LH and testosterone and comb height increased more slowly in Svalbard than in willow ptarmigan as daylength increased. In both species, plasma LH and testosterone fell abruptly, and the supraorbital combs regressed in June, marking the development of long-day refractoriness. Comparison with free-living Svalbard ptarmigan ( K.-A. Stokkan, P. J. Sharp, and S. Unander (1986) Gen. Comp. Endocrinol. 61, 446–451) at 80°N, showed a similar slow increase in reproductive function before the onset of the breeding season. However, maximum plasma LH levels and comb size were higher in free-living than in captive Svalbard ptarmigan. Furthermore, long-day refractoriness developed earlier in captive than in free-living Svalbard ptarmigan. In both species of ptarmigan, the development of long-day refractoriness was associated with increased plasma prolactin. This increase was larger and occurred earlier in the Svalbard than in the willow ptarmigan. Seasonal changes in thyroid hormones were not as marked as for the other hormones measured. In both species, plasma T 4 tended to increase and plasma T 3 to decrease as daylength increased. A small increase in plasma T 3 was seen after the development of long-day refractoriness in both species. It is concluded that captivity depresses the photoperiodic response of Svalbard ptarmigan more than that of willow ptarmigan. The association between increased plasma prolactin and the development of long-day refractoriness is similar to that reported for birds in other families. The changes in plasma thyroid hormones during the development of refractoriness cannot be readily related to changes seen in other species.

Sequential Changes in Plasma Luteinizing Hormone and Plasma Prorenin during the Menstrual Cycle

SEALEY, JEAN E.; CHOLST, INA; GLORIOSO, NICOLA; TROFFA, CHIARA; WEINTRAUB, ILENE D.; JAMES, GARY; LARAGH, JOHN H. Author Information

Sequential Changes in Plasma Luteinizing Hormone and Plasma Prorenin during the Menstrual Cycle

SEALEY, JEAN E.; CHOLST, INA; GLORIOSO, NICOLA; TROFFA, CHIARA; WEINTRAUB, ILENE D.; JAMES, GARY; LARAGH, JOHN H.Author Information

Sequential changes in plasma luteinizing hormone and plasma prorenin during the menstrual cycle.

Prorenin, the enzymatically inactive biosynthetic precursor of renin, is secreted by the kidneys. However, the ovaries appear to be the source of the cyclical increase in plasma prorenin that occurs in the middle of the menstrual cycle. In this study we examined the temporal relationship between changes in plasma prorenin and LH in normal women to determine whether ovarian prorenin secretion might be stimulated by LH. Blood was collected from nine normal women daily for 7 days in the midcycle period and from six of them every 8 h on 6 of these days. Time zero was taken as the highest plasma LH value. The initial rise in LH (-24 h) preceded the initial rise in prorenin (-8 h) and the LH peak preceded the prorenin peak by 8-16 h. These sequential increases in plasma LH and prorenin occurred in the presence of high plasma estradiol levels. While LH fell in parallel with estradiol, the prorenin peak was more sustained and plasma prorenin remained above baseline at 40 and 48 h, at a time when both estradiol and LH had reached a new basal level. These results suggest that gonadotropins stimulate ovarian prorenin release. The timing of the changes in plasma prorenin and its presence in high concentrations in ovarian follicular fluid suggest that prorenin may be involved in the process of ovulation. The results also suggest that changes in plasma prorenin may determine the activity of an ovarian renin system that functions independently of circulating active renin.