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PubMed1977

[The mechanism of follicle growth. II. The mode of action of the follicle-stimulating hormone (FSH) on follicle growth (author's transl)].

The mode of action of the follicle-stimulating hormone (FSH) on ovarian follicle growth was studied in hypophysectomized rats using the histologic, autoradiographic and histochemical techniques. The follicle growth was stimulated by the administration of both FSH and estrogen. The histologic finding of the follicle growth induced by the two hormones was different. Namely, after the administration of FSH, the theca layer was thick, but after the administration of estrogen, it was thin. 3H-thymidine and 3H-leucine were used to investigate cell division in a growing follicle. The uptake of 3H-thymidine and 3H-leucine by the theca layer was enhanced remarkably by FSH. On the other hand, the uptake of 3H-thymidine by the granulosa layer was enhanced by FSH or estrogen, while the grain count of granulosa cells was increased only by the administration of estrogen. Moreover, the administration of FSH resulted in an increase of the enzyme activity of glucose-6-phosphate dehydrogenase (G-6-PD), DELTA5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) and alkaline phosphatase (ALPase) in the theca layer. Furthermore, the administration of FSH caused an increase in the serum estradiol and estriol of rats, whereas the administration of estrogen did not. It seems possible, therefore, that FSH stimulated proliferation of theca cells and produced estrogen. The results suggest that the estrogen produced by the theca cells might stimulate proliferation of granulosa cells; consequently, follicle growth might be induced.

Animals↗
PubMed1975

Quick release of FSH stimulated by repeated applications of synthetic luteinizing hormone-releasing hormone (LH-RH) in immature male rats.

Serum FSH and LH levels were estimated by radioimmunoassay following single subcutaneous administration, and repeated subcutaneous administration at various intervals in immature male rats. Single injection of LH-RH induced slight increase in FSH levels in comparison with considerable increase in LH. By two successive injections, the release of FSH was markedly stimulated when the time intervals were 15, 30, and 60 minutes,and rapidly elicited to release after the second injection. The greatest response was observed by two injections at 60 minutes interval. Moreover, the elevation of serum FSH level after the third injection was particularly remarkable, and the response was much stronger than that to the second injection. On the other hand, serum LH levels following the repeated injections were quite similar to that of FSH. And both FSH and LHwere linearly responded to doses of LH-RH repeatedly administered. These results indicated that the repeated quick administrations of LH-RH under appropriate intervals caused the acute high release of FSH, which was quite similar to LH release, and that these acute release of FSH and LH showed the dose-response relationship.

Animals↗
PubMed1978

Effect of steroids in combination with LH-RH on the release of LH and FSH in LH-RH-primed immature male rat.

LH and FSH release of immature male rats was remarkedably enhanced by LH-RH if primed with LH-RH one hour before. The effect of exogenous steroids on the action of the second LH-RH was investigated. C-18, C-19 and C-21 steroids in different doses were tested. Blood samples were collected from the jugular vein immediately before and 30 min after the second LH-RH injection. Serum LH and FSH were determined by respective radioimmunoassays. The concomitant increase of LH and FSH was not induced by all the steroids administered iv. Estrone or 17alpha-hydroxyprogesterone suppressed LH and FSH release. Estradiol-17beta preferentially suppressed LH release. Cortisone, progesterone or dehydroepiandrosterone significantly facilitated FSH release, whiel 20alpha-dihydroprogesterone or 20beta-dihydroprogesterone selectively promoted LH release. The sc injection of most steroids dissolved in oil tended to augment the acute release of LH but not FSH. 20alpha-Dihydroprogesterone was particularly potent in this concern. Dehydroepiandrosterone or androstenedione was effective in maintaining FSH release for a longer period. These data revealed that potentiated LH and FSH release induced by the second LH-RH was readily modified by steroids administered simultaneously.

Androgens↗
PubMed1976

Radioligand receptor assay of FSH.

The assay of FSH by a radioligand receptor assay (RLA) using homogenates of rat testicular tissue incubated for 17 h at 21 degrees C has been assessed. Chloramine-T or lactoperoxidase were used for iodination. The assay gave linear dose-response lines between 30 and 2000 ng sheep FSH/tube, and there was usually no major interference by LH. Two batches of labelled FSH, however, gave assays in which LH showed a striking interaction with FSH. When these batches were avoided and FSH and LH were mixed in ratios that differed less than fourfold, the assay was combined successfully, in the same tubes, with an RLA for LH, using LH and FSH labelled with 131I and 125I respectively. The RLA for FSH was not suitable for assay of FSH in rat serum because of apparent non-specific interference. Assay by RLA of rat FSH, in pituitary homogenates or released during incubation in vitro, gave results which were not closely correlated with those of either conventional bioassay or radioimmunoassay.

Animals↗
PubMed1976

Effect of an anabolic steroid (metandienon) on plasma LH-FSH, and testosterone and on the response to intravenous administration of LRH.

Plasma levels of testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as well as the response of LH and FSH to the intravenous administration of 100 mug of luteinizing hormone releasing hormone (LRH) were measured in 16 well-trained athletes (mean age 30 years) before and after 2 months of daily oral intake of 15 mg of metandienon, and anabolic steroid (Anabolin, 17 alpha-methyl-17beta-hydroxy-1,4-androstadien-3-one, Medica, Finland). All athletes continued to train regularly, just as they had done for several years. During administration of metandienon the mean plasma testosterone level fell 69%, from 29.4 +/- 11.6 nmol/1 to 9.1 +/- 7.5 nmol/1. The mean plasma levels of LH and FSH also fell significantly (P less than 0.001 and P less than 0.01, respectively), both about 50%. Because LH and FSH levels were low after administration of the steroid the maximum stimulation values after LRH administration were also lower than pre-treatment values although the mean increments did not differ significantly before and after administration of the anabolic steroid. However, after treatment, the FSH response curve had a biphasic pattern in most subjects, with peaks at 10 to 20 and 50 to 60 min after the iv injection of LRH. Administration of LRH after the treatment period had no effect on FSH secretion in two subjects and no effect on LH secretion in one. Our results show that administration of an anabolic steroid causes a pronounced lowering of plasma levels of testosterone, LH and FSH but causes no gross alteration in the response of LH secretion to stimulation by LRH. The reason for the biphasic response pattern of FSH to LRH administration in most subjects is not known.

Adult↗
PubMed1987

Evidence for diverse structural variations of the forms of human FSH within and between pituitaries.

The biological activity of FSH in vitro (B-vitro) was compared with its radioimmunological (RIA) activity in 38 pituitary extracts from men and women. The B-vitro method was based upon the estimation of oestradiol produced by cultured Sertoli cells from 10-day-old rats. The mean B-vitro/RIA ratios for FSH of men and young and elderly women were almost identical. The mean values of median charge of the forms of FSH differed significantly between the three groups of human adults. The B-vitro/RIA ratio of different forms of FSH, separated by electrophoresis of 14 individual pituitary extracts, was higher for less negatively charged than for more negatively charged forms. Some forms of FSH with the same charge and separated from different pituitary extracts, e.g. from a young and an elderly woman, had significantly different B-vitro/RIA ratios. This ratio, thus, was not related to the charge per se of the hormone. However, the relation between the B-vitro/RIA ratio and the charge of FSH was similar for individual pituitary extracts when charge was expressed in relation to median charge. The results suggest that different molecular structural variations of FSH are involved in the polymorphisms observed within and between individual pituitaries. In human adults, the variation of FSH between the pituitaries mainly affects the metabolic clearance rate (MCR) of the hormone, whereas the variation within the individual pituitary affects both the MCR of the hormone and its biological effect at the target cell.

Adolescent↗
PubMed2002

Inhibin B plasma concentrations in infertile patients with DAZ gene deletions treated with FSH.

OBJECTIVE: The DAZ (deleted in azoospermia) gene family on the Y chromosome long arm is the major candidate for the AZFc (azoospermia factor c) phenotype of male infertility and it is expressed only in germ cells. The aim of the study was to assess Sertoli cell function in subjects with AZFc deletions. DESIGN: Case-control, prospective study. METHODS: We have studied six severely oligozoospermic subjects with AZFc-DAZ deletions, and looked whether they responded in terms of inhibin B production to a 1 month FSH treatment. These patients were compared with three groups of patients affected by different spermatogenic alterations not related to deletions on the Y chromosome. RESULTS: Although affected by severe testiculopathy, patients with AZFc-DAZ deletions had only slightly elevated FSH, and normal inhibin B plasma concentrations. Inhibin B responded normally during FSH treatment, supporting the hypothesis that Sertoli cells are not altered. On the contrary, other severe testiculopathies not related to Y chromosome deletions showed high FSH and low inhibin B concentrations, with no response to FSH treatment. In these cases the cause of the spermatogenic defect probably damaged both germ and Sertoli cells. Finally, idiopathic patients with a hormonal status similar to Y-deleted patients (slightly elevated FSH and normal inhibin B concentrations) did not respond to FSH treatment, suggesting that Sertoli cells were already at their maximal functional capability. CONCLUSIONS: These data confirm that Sertoli cell function is not damaged in patients with AZFc-DAZ deletions and that the strong reduction of germ cells does not affect the FSH-inhibin B feedback loop.

Adult↗
PubMed1978

The temporal relationship between plasma levels of FSH and LH in the ram.

Blood samples were collected from adult Soay rams at frequent intervals during the regressed, developing and active phases of the sexual cycle, or after i.v. injections of synthetic LH-RH or standard preparations of ovine FSH and LH, and were assayed for FSH, LH and testosterone. The highest FSH and LH levels occurred during the developing stage of the cycle, and the highest testosterone levels during the active stage. At each phase there were conspicuous short-term fluctuations in the concentrations of all three hormones, and episodic peaks of plasma LH were associated with increases in both FSH and testosterone. Synthetic LH-RH (5 microgram) induced a rise in the plasma values of FSH and LH at all stages and the magnitude and duration of the response could be predicted from a knowledge of the endogenous short-term fluctuations. When 50--250 ng LH-RH were given i.v. plasma LH increased in a way similar to that occurring spontaneously. The ratio of FSH:LH released after LH-RH changed with the stage of the sexual cycle, but the clearance rate of the two hormones was not affected. These findings are consistent with the control of FSH and LH by a single releasing hormone which is secreted in pulses. The different temporal patterns in the circulating FSH and LH result from differences in secretion and clearance.

Animals↗
PubMed1979

LH contamination may explain FSH effects on rat Leydig cells.

Treatment of immature, hypophysectomized male rats with 50 micrograms ovine FSH (NIH-FSH-S12) twice a day for 5 days stimulated the maximum quantity of 17 beta-hydroxyandrogen produced by isolated Leydig cells in response to hCG. Pretreatment of the FSH preparation with an LH antiserum in one study markedly reduced and in another study completely abolished this stimulatory effect of FSH, but only slightly impaired the capacity of the hormone to stimulate the Sertoli cell in vivo (epididymal androgen-binding protein). Administration of another highly potent FSH preparation (LER-1881) had no discernible effects on the dose-response characteristics of the Leydig cells but was superior to the NIH-FSH-S12 in its capacity for stimulating the Sertoli cell. When all hormone preparations were tested for their ability to stimulate steroid secretion from normal Leydig cells in vitro, a close correlation was obtained between their Leydig cell-stimulating activity (a measure of LH contamination) and their capacity to alter Leydig cell responsiveness after in-vivo treatment. FSH treatment had no effects on specific LH binding per 10(6) Leydig cells. It is concluded that the stimulatory influence of FSH on rat Leydig cells may to some extent be a result of the LH contaminating the hormone preparation.

Androgens↗
PubMed1985

Time series analysis of plasma LH and FSH concentrations as a method of assessing episodic secretion.

Time series analysis was used to detect LH and FSH episodes in untreated seasonally anoestrous ewes and prepubertal heifers, and in these animals when treated with low doses of GnRH. For comparison, these profiles were also assessed for episodic secretion by subjective, visual appraisal methods and by cycle detection-an objective threshold method. In untreated animals, time series analysis detected recurring events in the LH and FSH profiles, the period lengths of which varied between individual animals. When GnRH was injected at 2-h intervals, cycles in LH secretion with period lengths of 120 min were recorded in all animals, of 60 min in all ewes and 11/12 heifers, and of 40.5 min in 22/24 ewes and 10/12 heifers. The cycles with period lengths of 60 and 40.5 min are probably artefacts of this method of analysis. No consistent cycles in FSH release were detected in GnRH-injected anoestrous ewes, but 120-min cycles were recorded in 8/12 GnRH-injected heifers. When GnRH was administered to seasonally anoestrous ewes by continuous infusion, recurring cycles in both LH and FSH secretion were evident. However, there was no consistency in their period lengths and the mean number and frequency of cycles were similar to pretreatment values. The number of episodes detected by visual appraisal was influenced by the choice of episode definition. Both methods identified LH, but not FSH, episodes in response to each injection in all GnRH-injected animals. Cycle detection, which does not identify individual episodes, recorded LH and FSH episode frequencies similar to those detected by the more stringent method of visual appraisal. Time series analysis detected an FSH response to GnRH injections in prepubertal heifers that was not identified by the other methods of analysis. However, because of the asymmetric nature of LH episodes, it also detected cycles in LH profiles that were probably spurious. Subjective decisions influenced the frequencies of LH and FSH episodes recorded by visual appraisal, and the variation in episode amplitude in these profiles made cycle detection inappropriate. Each of these methods can contribute to the interpretation of hormone profiles, but their constraints and limitations must be recognized.

Anestrus↗
PubMed1988

Microfilaments and FSH stimulation of rat granulosa cell steroidogenesis in vitro.

The secretion of progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-dihydroprogesterone) by granulosa cells from 30-day-old rats pretreated with PMSG (4 i.u.; i.p.) was significantly increased in a time- and concentration-dependent manner by FSH or cytochalasin B. Whereas FSH markedly stimulated progestagen secretion during 3 h of incubation, a significant enhancement of the steroidogenic response was not noted until 12 h of exposure to the inhibitor in vitro. Although cytochalasin B also enhanced the submaximal stimulation of progestagen production by FSH (15 ng/ml), it was ineffective in the presence of maximal stimulatory concentration of the gonadotrophin (150 ng/nl). With increasing concentrations of cytochalasin B, the ability of FSH to further stimulate progestagen secretion was progressively reduced. Granulosa cells cultured in medium alone contained a prominent cytoplasmic array of microfilaments which was markedly reduced by FSH or cytochalasin B. FSH and, to a greater extent, cytochalasin B elicited concentration-dependent reductions in the mean area occupied by the cells on the culture surface, the contour index (a size-independent representation of cell profile irregularity) and cell perimeter, indicating that the cells underwent less spreading and were more spherical and regular in outline in the presence of either agent. The FSH-induced reductions in the three shape-related parameters were augmented by cytochalasin B although the influence of the FSH on the mean area and perimeter was progressively reduced in the presence of higher concentrations of cytochalasin B.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1988

Consequences of increasing or decreasing plasma FSH concentrations during the preovulatory period in Romney ewes.

Romney ewes were infused with ovine FSH (NIADDK-oFSH-16) for 48 h from the initiation of luteolysis with cloprostenol. Doses of 2.5 or 5 micrograms/h which partly or completely prevented the normal preovulatory decline in plasma FSH concentrations caused a significant increase in mean ovulation rates. Ovulation rates were not increased significantly if the FSH (5 micrograms/h) was infused for only 20 h starting from the initiation of luteolysis or 24 h later. Infusion of a less potent and relatively impure preparation of FSH (i.e. FSH-P) at 0.5 mg/h for 48 h after cloprostenol treatment also increased the mean ovulation rate significantly. However, if the FSH-P was given for only the first 24 h, or if the start of the infusion was delayed for more than 12 h, mean ovulation rates were not increased significantly. Infusion of LH (NIADDK-oLH-25, 5 micrograms/h) for 48 h from the initiation of luteolysis decreased the mean ovulation rate significantly. Administration of bovine follicular fluid to suppress plasma FSH concentrations below normal during the first 24 h after cloprostenol injection did not delay oestrus. However, oestrus was delayed by approximately 2 days if plasma FSH concentrations were reduced by bovine follicular fluid 24 h after the initiation of luteolysis. As ovulation rate increased, the mean weight of individual corpora lutea of each ewe decreased. In ewes with a single ovulation, most corpora lutea weighed greater than 600 mg, but as the ovulation rate increased the proportion of corpora lutea present weighing less than 400 mg rose steadily.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

FSH concentrations and sensitivity to feedback in infant lambs from breeds differing in prolificacy.

Plasma FSH concentration was significantly higher in Romanov than Ile-de-France ewe lambs at 5, 6 and 7 weeks of age (P less than 0.001, P less than 0.02 and P less than 0.02, respectively) and at 5, 6 and 7 weeks of age (P less than 0.001, P less than 0.01 and P less than 0.05, respectively) compared to Finn lambs. FSH concentrations were similar and unaffected by time in Ile-de-France and Finn lambs. Ovariectomy at 5 weeks of age produced similar increases in FSH concentrations in Romanov and Ile-de-France ewe lambs, but at 3 months of age the increase in FSH concentrations after ovariectomy was significantly steeper (P less than 0.02) in Romanov than Ile-de-France lambs. Sensitivity to oestradiol feedback was related to the age of the lambs. At 5 weeks of age, oestradiol (30 micrograms in oil per lamb) produced a significant decrease (P less than 0.001) in FSH concentrations in Romanov and Ile-de-France lambs, demonstrating that negative feedback can be triggered by oestradiol at this age. Positive feedback after an oestradiol challenge was identified in lambs of both breeds at 6 weeks of age. Sensitivity to the negative feedback of follicular fluid compounds was also established at 5-6 weeks and did not differ between breeds. At 9-10 weeks of age, while there was no breed effect of an oestradiol challenge on FSH concentrations, suppression of FSH concentrations by follicular fluid was shorter in Finn than in the other lambs. As all the feedback mechanisms are functional at 5-6 weeks of age, it is likely that the between breed differences of FSH profile during infancy are linked to differences in gonadal development.

Animals↗
PubMed1993

FSH-stimulated follicle development in ewes in high and low body condition and chronically treated with gonadotrophin-releasing hormone agonist.

Ovarian follicle development in response to FSH infusion was investigated in Scottish Blackface ewes with high and low body condition scores in which endogenous gonadotrophin secretion and follicle development to > or = 2.5 mm diameter was suppressed using subcutaneous implants containing a GnRH agonist. In two experiments conducted during the normal breeding season, groups of 20 (Expt 1) and 15 (Expt 2) ewes were fed to achieve body condition scores > or = 2.75 (high; H) or < or = 1.75 (low; L). In both experiments GnRH agonist implants were inserted four weeks before FSH was infused for 72 h at 7 micrograms h-1 to group H animals or at 5 micrograms h-1 to group L animals; the infusion rates were designed to ensure similar circulating FSH concentrations in animals of both groups. In Expt 2, additional subcutaneous implants containing oestradiol were inserted 21 days after insertion of GnRH agonist implants and 7 days before the FSH infusion began. In both experiments, FSH infusion was associated with an increase in circulatory concentrations of LH (P < 0.01) and FSH (P < 0.001), but there was no difference with body condition in mean circulating gonadotrophin concentrations, the numbers of ovarian follicles > or = 2.5 mm diameter, the proportion of these follicles that were oestrogenic or the mean rate of oestradiol secretion in vitro. It is concluded that differences in body condition of ewes do not affect the responsiveness of the ovary to FSH, in the presence or absence of oestradiol, as measured by the number, size and steroidogenic capacity of ovarian follicles present following FSH infusion.

Animals↗
PubMed1993

Effects of ovariectomy and genotype on bioactive FSH in plasma and pituitary of Booroola ewes.

Blood samples were collected for 13 days before and 20 days after ovariectomy from carrier (BB) and non-carrier (+ +) ewes of the Booroola FecB gene (n = 12 per genotype), at known stages of the oestrous cycle, after which the pituitary glands from these ewes were recovered. Pituitary glands were also collected from cyclic ewes (about day 12; n = 5 per genotype) to compare the effects of ovariectomy on pituitary gonadotrophins. Plasma samples and pituitary extracts were assayed for bioactive (B) FSH, immunoreactive (I) FSH and I-LH. Overall, BB ewes had significantly (P < 0.05) higher plasma I-FSH concentrations than did + + ewes before ovariectomy; the mean value was higher on 16 of the 17 days of the oestrous cycle (P < 0.01). For B-FSH, there were no overall genotypic differences, although the mean for the BB ewes was significantly higher on 13 of the 17 days of the oestrous cycle (P < 0.05), and significantly (P < 0.05) higher between days 13 and 16. No genotypic differences were noted for the plasma bioactive:immunoreactive (B:I) ratio for FSH before ovariectomy. After ovariectomy, there were significant (P < 0.001) increases in plasma for B-FSH, I-FSH and I-LH and a significant (P < 0.05) decrease in the B:I ratio for FSH, irrespective of genotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of ovariectomy and FecBB genotype on the median charge and circulating half-life of pituitary FSH isoforms of ewes.

This study investigated the effects of short-term (20 days) ovariectomy, the effects of FSH assay (radioimmunoassay, receptor assay or in vitro bioassay) and of FecBB genotype on the characteristics of pituitary FSH from Booroola ewes. Pituitary extracts were obtained from ovariectomized homozygous carriers (BB) and non-carriers (++, n = 8 per genotype) and ovary-intact controls (n = 4 per genotype). The extracts (n = 4 per genotype per treatment) were subjected to agarose suspension electrophoresis and the eluates were assayed by the three FSH methods. There were significant effects of ovariectomy (P < 0.01) and assay system (P < 0.05) but not of genotype on the median charge of FSH isoforms. The mean +/- SEM migration rates for FSH in intact and ovariectomized ewes were 0.469 +/- 0.006 and 0.439 +/- 0.006 albumin mobility units, respectively (P < 0.01), indicating a shift to more basic isoforms after short-term ovariectomy. When the pituitary extracts were subjected to anion-exchange HPLC, there was a significant (P < 0.01) shift to more basic isoforms in the ovariectomized ewes as shown using agarose electrophoresis, and no gene effects were noted. When the pituitary extracts (n = 4-8 per group) were injected into mature female mice, there were no significant effects of ovariectomy or genotype on the circulating half-lives of the pituitary FSH isoforms. These results indicate that after short-term ovariectomy, the increase in plasma FSH concentrations is accompanied by a shift in the median charge of pituitary FSH isoforms without any observable change in their metabolic clearance rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Relationships between FSH and ovarian follicular waves during the last six months of pregnancy in cattle.

Follicles were monitored daily by ultrasound and blood samples for FSH assay were collected daily from eight heifers from day 90 of pregnancy to the emergence of the first postpartum follicular wave. Follicles > or = 6 mm in diameter emerged in groups or waves in each heifer (P < 0.005). Follicular waves developed rhythmically throughout pregnancy, except that follicles > or = 6 mm were not detected during the last 21.6 +/- 2.4 (mean +/- SEM) days of pregnancy. The characteristics of the first follicular wave after day 90 were similar to previous reports for days 10-100. However, between months 4 (days 90-119) and 5, there was a decrease (P < 0.05) in monthly means for maximum diameter (mm) of largest (21.1 +/- 0.5 versus 9.5 +/- 0.5) and second largest (8.0 +/- 0.3 versus 6.9 +/- 0.2) follicles, duration of the interwave interval (8.1 +/- 0.4 versus 6.6 +/- 0.3 days), and number of follicles per wave (3.7 +/- 0.4 versus 2.5 +/- 0.4). Averaged over all follicular waves during months 4-9, the concentrations of FSH normalized to the emergence of a follicular wave increased (P < 0.05) over the 3 days before emergence, reached peak values on the day of emergence of the future dominant follicle at 4 mm, and decreased (P < 0.05) over the 3 days following emergence. Surges in FSH concentrations occurred throughout pregnancy, but during the last 30 days of pregnancy the number of surges was reduced and each heifer had one or two ineffective surges (no follicular wave detected). The temporal relationship between FSH surges and emergence of waves was closer (P < 0.01) than would be expected if the two events were independent. Surges of FSH occurred rhythmically even when there was no follicular response (no follicle > 5 mm). In association with waves in which the largest follicle reached > or = 10 mm compared with 6-9 mm, there was greater depression in the FSH nadir, longer intervals from FSH peak to nadir, and longer intervals between adjacent FSH peaks and adjacent waves.

Animals↗
PubMed1993

The role of inhibin on pituitary FSH secretion and maturation of pituitary-gonadal axis in immature female rats.

The possible physiological significance of endogenous inhibin was evaluated in prepubertal female rats during sexual maturation. Ovarian/serum inhibin, serum FSH levels were measured from 4th day to 35th day of life by RIA. Serum inhibin levels were first detected on 4th day of life, thereafter, progressively increasing up to 27th day. Serum FSH levels gradually increased up to the 14th day with a sharp fall in the FSH levels on day 15 which afterwards was maintained at a lower level. Pregnant mare serum gonadotropin (PMSG) treatment on day 14 and day 22 rats showed different patterns of serum FSH and inhibin changes. In 14 day group, there was no difference between control and PMSG treatment, but in 22 day group, not only significant difference between control and PMSG treatment but also inverted relations between FSH and inhibin after PMSG treatment were found. It can be postulated from these findings that secretion of inhibin from the granulosa cells is initiated by FSH by its direct action on the ovary whereas the level of FSH itself is controlled by inhibin after FSH reaches peak values. Also it can be inferred that the feedback control mechanism of inhibin seems to be established around 3rd week of life.

Animals↗