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PubMed1994

Localization of follicle-stimulating hormone (FSH) immunoreactivity and hormone receptor mRNA in testicular tissue of infertile men.

Testicular biopsies from 82 oligo- or azoo-spermic male patients were subjected to immunostaining using anti-human FSH antibodies. Histological evaluation showed normal spermatogenesis (nspg) in 7 (FSH: (2.7 +/- 0.7), mixed atrophy (ma) in 63 (FSH:L 5.3 +/- 0.5), and bilateral or unilateral Sertoli Cell Only syndrome (SCO) in 12 (FSH: 21.7 +/- 3.5) patients. For the relationship between FSH values and testicular histology, see Bergmann et al. (1994). FSH immunoreactivity was found exclusively in Sertoli cells and in some interstitial cells. Seminiferous epithelium showing normal or impaired spermatogenesis displayed only weak immunoreactivity compared to intense immunoreaction, i.e. large and numerous vesicles in Sertoli cells of SCO tubules in biopsies showing mixed atrophy or SCO. In addition, h-FSH receptor mRNA was demonstrated by in situ hybridization using biotinylated cDNA antisense oligonucleotides. Hybridization signals were found within the seminiferous epithelium exclusively in Sertoli cell cytoplasm associated with normal spermatogenesis and in epithelia showing different signs of impairment, including SCO. It is concluded that: (1) Sertoli cells are the only cells within the seminiferous epithelium expressing FSH receptors; (2) the accumulation of FSH immunoreactivity in Sertoli cells of SCO tubules appears to be a sign of impaired Sertoli cell function.

Adult↗
PubMed1993

Expression of the FSH receptor in the testis.

FSH has multiple and changing roles in the regulation of spermatogenesis. The first function of FSH is to increase the number of Sertoli cells by stimulation of their mitotic activity. During the prepubertal phase of development, FSH is important for the maturation of the Sertoli cells. Hormonal stimulation of tight junction formation and specific protein secretion are essential. In the adult rat, some of the functions carried out by FSH in prepubertal animals are assumed by testosterone. However, there is evidence that even in the adult rat, FSH is important for quantitatively normal spermatogenesis. The gene for the FSH receptor is large (greater than 85 kb) and complex (10 introns) and is structurally similar to the genes for the LH and TSH receptor. The promoter region of the FSHR gene has been identified and is active in the expression of transgenes in transfected Sertoli cells. We have shown that the FSH receptor mRNA is present in the testes of the adult rat and that the levels of this mRNA are changing during the cycle of the seminiferous epithelium. The presence of relatively high levels of FSHR mRNA in stages XIV-II of the cycle and the relatively low levels in stages VII-VIII suggest that the FSH receptor is carefully regulated in adult rats and presumably has an important function in spermatogenesis. The levels of FSHR mRNA in cultured Sertoli cells are immediately reduced in the presence of FSH or phorbol esters, but the levels soon return to normal.

Animals↗
PubMed2006

FSH receptor genotype is associated with pregnancy but not with ovarian response in IVF.

Two very common single nucleotide polymorphisms at positions 307 and 680 in exon 10 of the FSH receptor gene have been associated with ovarian response in IVF. This observational study evaluated the role of the FSH receptor genotype in the prediction of poor response and clinical pregnancy in IVF in comparison with other markers, such as age, basal FSH, anti-Müllerian hormone and antral follicle count. In addition, the in-vitro cAMP response towards recombinant FSH in cultured granulosa cells of patients with different FSH receptor genotypes was determined. A total of 105 IVF patients undergoing ovarian stimulation in a long suppression protocol were included in the study. The ovarian response was comparable between patients with different FSH receptor genotypes. Patients with polymorphism Ser/Ser had implantation and pregnancy rates that were three times higher compared with patients with polymorphism Asn/Asn. FSH receptor genotype was not associated with a poor response in IVF, but showed a positive association with pregnancy, independent of age. There was no difference in cAMP production in cultured granulosa cells of patients with different FSH receptor genotypes (n=62). It is concluded that FSH receptor genotype is associated with pregnancy in IVF, but not with ovarian response.

Adult↗
PubMed1992

Evidence that the FSH receptor itself is not a calcium channel.

FSH has been shown to stimulate the uptake of calcium in cultured rat Sertoli cells, resulting in an increase in cytosolic calcium concentrations. One possibility which has been put forth is that the FSH receptor per se may act as a calcium channel. This is all the more tantalizing given the proposed structure of this receptor which, like all other G protein-coupled receptors, is thought to have the putative transmembrane helices forming a bundle-like structure in the plasma membrane. To test whether the FSH receptor could function as a calcium channel, we performed whole-cell voltage clamp experiments on 293 and 293F(wt1) cells, which are a clonal line of 293 cells expressing high levels of rat FSH receptors. The 293 cells, which do not express FSH receptors, were found to lack any detectable inward calcium currents, and therefore, serve as an excellent model for transfecting with potential calcium conducting FSH receptors. When the 293F(wt1) cells were then tested, no inward calcium currents could be detected in either control or FSH-stimulated cells. These results suggest that the FSH receptor itself is not a calcium channel and, therefore, FSH must be stimulating endogenous calcium channels in rat Sertoli cell plasma membranes.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

Biopotency of highly purified porcine FSH and human LH on gonadal function.

The gonadotrophin preparations that have been used previously to study different aspects of testis function are of limited purity. We have, therefore, purified existing gonadotrophin preparations further. The demonstration of their purity and biological activity are reported as well as their suitability for in-vivo use. After separation of the subunits of the intact hormones by high-performance liquid chromatography followed by analytical sodium dodecylsulphate-polyacrylamide gel electrophoresis, no contaminating proteins could be detected in either the FSH or LH preparation. After immunoadsorption, contamination by other pituitary hormones (TSH, prolactin, FSH, LH and GH) was found to be less than 0.002% by weight for all the hormones tested. The biological activity of porcine FSH (pFSH) measured in a Steelman-Pohley assay was 150-170 times more potent than the NIH-FSH-P1 reference preparation. The biopotency of human LH (hLH) in the ovarian ascorbic acid depletion test was measured and appeared to be 8100-8300 IU/mg against the 68/40 International Standard. The dose-dependent effects of pFSH and hLH on testis weight and the number of FSH and LH receptors were measured in immature (22-day-old) hypophysectomized rats treated for 7 consecutive days. Treatment with FSH induced a dose-dependent increase in testis weight (threefold) when compared with the control. The concentration and total number of LH receptors were increased (two- to sixfold) in a dose-dependent manner. The number of FSH receptors per testis increased while the number of FSH receptors per mg of protein remained unchanged. Administration of human LH to immature hypophysectomized rats had no effect on either LH or FSH receptors, regardless of the dose administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Functional expression of the recombinant human FSH receptor.

The functional capacity of the recombinant human FSH (hFSH) receptor was tested on the basis of gonadotrophin stimulation of cyclic AMP (cAMP) production by transient transfections of 293 cells and stable transfections of Chinese hamster ovary (CHO) cells. A CHO cell line expressed with the hFSH receptor cDNA covering the entire amino acid coding region revealed the presence of FSH binding site (Kd 6.2 x 10(-10) M) on the plasma membrane. Treatment of transfected cells with hFSH induced dose-dependent increases in intracellular cAMP production. These results indicate that the hFSH receptor functionally couples with endogenous adenylyl cyclase. Although rat FSH also induced dose-dependent increases in cAMP production, bovine FSH was effective only at high doses and human chorionic gonadotropin did not alter cAMP levels compared with control values. Northern blot analysis with a cRNA probe derived from hFSH receptor cDNA indicated the presence of two common FSH receptor mRNA transcripts (2.4 and 4.1 kb) in RNA prepared from a human ovary and transfected cell lines. Preincubation of CHO cells expressing a functional hFSH receptor (CHO-FSHR) with FSH for 16 h decreased the subsequent cAMP production resulting from a 30-min pulse of FSH stimulation. These results indicate that desensitization of the adenylyl cyclase response to FSH stimulation occurs in CHO-FSHR cells. This cell line therefore provides a tool with which to pursue detailed studies on the molecular basis of FSH-induced desensitization.

Animals↗
PubMed2006

G protein-coupled receptor kinase 2 and beta-arrestins are recruited to FSH receptor in stimulated rat primary Sertoli cells.

FSH-receptor (FSH-R) signaling is regulated by agonist-induced desensitization and internalization. It has been shown, in a variety of overexpression systems, that G protein-coupled receptor kinases (GRKs) phosphorylate the activated FSH-R, promote beta-arrestin recruitment and ultimately lead to internalization. The accuracy of this mechanism has not yet been demonstrated in cells expressing these different molecules at physiological levels. Using sucrose gradient fractionation, we show that FSH induces the recruitment of the endogenous GRK 2 and beta-arrestin 1/2 from the cytoplasm to the plasma membrane of rat primary Sertoli cells. As assessed by ligand binding, the FSH-R was found expressed in the fractions where GRK 2 and beta-arrestins were recruited upon FSH treatment. In addition, the endogenous beta-arrestin 1 was found dephosphorylated in an agonist-dependent manner. Finally, a significant FSH-binding activity was co-immunoprecipitated with the endogenous beta-arrestins from agonist-stimulated but not from untreated Sertoli cell extracts. This FSH-R interaction with beta-arrestins was sustained for up to 30 min. In conclusion, our data strongly suggest that the GRK/beta-arrestin machinery plays a physiologically relevant role in the regulation of the FSH signaling.

Animals↗
PubMed1981

The effect of ionic environment in specific FSH binding to plasma membrane receptor.

Studies were undertaken to define the effects of ionic strength and ion selectivity on specific binding of 125I-hFSH to both its particulate and Triton X-100 solubilized calf testis plasma membrane receptor. Plasma membrane vesicles migrated with a negative charge on free flow electrophoresis. There was no evidence of formation of inside-out vesicles. Specific FSH binding to the plasma membrane vesicles with both monovalent and divalent cations, used to reduce charge repulsion between the negatively charged FSH molecule and membrane vesicles, revealed similar binding maxima at an ionic strength range of 0.03 to 0.05. However, Mg2+ consistently resulted in 25-30% greater specific binding than with any other cation. That increased FSH binding suggested unmasking of specific FSH plasma membrane binding sites. However, specific FSH binding to solubilized plasma membrane vesicles was unaffected by ionic strength or ion selectivity. Enzymatic removal of sialic acid from plasma membrane vesicles significantly enhanced specific FSH binding. In previous studies, we had observed that sialic acid was not exposed within the FSH binding site. Consequently, enhanced FSH binding associated with desialylation of plasma membrane vesicles probably reflected modification of parareceptor sites which affected the conformation of the specific FSH receptor.

Adenine Nucleotides↗
PubMedDate not supplied

Low molecular weight FSH binding inhibitor in bovine testis.

Purification of low Mr (less than 5000) inhibitors of FSH binding to receptors has been hampered by their low concentration in tissue extracts and physiologic fluids. The calf testis represents an accessible and economic source of large quantities of tissue, and was therefore studied as a source of FSH binding inhibitors. Supernatants (27,000 X g) of calf testis homogenates inhibited binding of [125I]-hFSH as well as [125I]-hCG to membrane-bound receptor from the same source. FSH binding inhibitor was concentrated from large volumes of testis supernatant by precipitation of inert material with metaphosphoric acid, concentration/desalting of the resulting supernatant by ultrafiltration (Amicon UM-05 membranes) and lyophilization. Separation of FSH binding inhibitor and LH(hCG) binding inhibitor activities could be achieved by molecular sieving on Sephadex G-25. A partially purified fraction with inhibitors of FSH binding activity (ED50 = 44 micrograms protein) and free of LH(hCG) binding inhibitor activity (no activity at 800 micrograms protein) emerged with a Ve/Vo of 1.9, reflecting an apparent Mr of about 1500. Inhibitors of LH(hCG) binding activity emerged with the column outer volume. Rechromatography of the FSH binding inhibitor fraction on G-25 indicated two closely associated peaks of activity. These could be further resolved by gel filtration through BioGel P2, to give a salt-free fraction with an FSH binding inhibitor activity (ED50) of 24 micrograms protein. The inhibitor was heat-labile, losing 80% of its activity after 2 hours at 100 C. The testicular low molecular weight FSH binding inhibitor is similar to bovine follicular fluid and serum FSH binding inhibitor by several parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Transferrin secretion in response to different modes of FSH stimulation and cycloheximide in superfused Sertoli cell cultures.

The influence of different modes of FSH stimulation and cycloheximide on transferrin secretion by rat Sertoli cells was investigated using a superfusion culture system. Sertoli cells from 18-day-old rats were cultured in serum-free medium on Matrigel-covered slides first in static conditions for 19 hours, and then superfused at a flow rate of 2.5 ml/hour. After an equilibration period of 48 hours to establish the basal rate of transferrin secretion, the cultures were exposed to various modes of FSH stimulation. Sertoli cells stimulated intermittently (20 min/2 hours) up to 22 hours responded to each consecutive FSH pulse with a rapid increase of transferrin secretion followed by a decline toward basal values. Continuous 22-hour exposure to FSH elicited an immediate increase followed by irregular fluctuations and a transient decline towards the baseline. With either mode of FSH stimulation, there was a secondary prolonged increase in transferrin secretion. Although cultures stimulated intermittently or continuously during the entire experimental period (22 hours) secreted similar cumulative amounts of transferrin (10.8 +/- 0.5 micrograms and 11.1 +/- 0.8 micrograms, respectively), there was a direct correlation between the secreted amount of transferrin and the duration of FSH exposure up to 8 hours. Addition of cycloheximide decreased both basal and FSH-stimulated transferrin secretion. However, even when cycloheximide was added 1 hour before FSH, an early secretory peak in response to FSH was still observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Immunohistochemical studies of human FSH producing pituitary adenomas.

Ten FSH producing pituitary adenomas were studied immunohistochemically. 9 cases were in males, and 7 showed elevated serum FSH levels. Immunohistochemically, all cases showed the presence of alpha-subunit and FSH-beta subunits in many tumour cells. These two subunits were frequently colocalized in the same cells. However, the expression of LH-beta subunit was extremely low (1 of 10 cases exhibiting occasional LH-beta positive tumour cells), although it has been reported that FSH-beta and LH-beta subunits are colocalized in the same cells of the normal adult pituitary gland. Immunoelectron microscopically, alpha-subunits and FSH-beta were present in the secretory granules and suggested the co-release of subunits or secretion of combined form of FSH. In 7 cases, TSH-beta was positive, and in some cases, TSH-beta was colocalized in the same tumour cells which contained alpha-subunit and FSH-beta subunit. A few cases also demonstrated immunoreactivity for PRL and ACTH. Our immunohistochemical studies suggest that FSH adenomas are multihormonal and that there is abnormal gene expression in FSH cells with loss of LH-beta appearance and co-expression of TSH-beta.

Adenoma↗
PubMed1989

Comparative binding of FSH to chicken and rat testis.

The binding characteristics of two highly purified preparations of follicle-stimulating hormone (FSH), one from equine (e) and one from porcine (p), were compared in a chicken testis radioreceptor assay. A two-component binding model was adequate to explain the binding of eFSH or pFSH to the chicken testis homogenate (CTH) FSH binding sites in the Scatchard study. The affinity of eFSH for the FSH binding site of CTH was 10-fold greater than that of pFSH by Scatchard analysis. This is consistent with the observation that in competitive protein binding studies approximately 10-fold greater quantities of pFSH were required to displace [125I] eFSH from the CTH FSH binding site than eFSH. Qualitatively, the order of relative potencies for various gonadotropin preparations was the same in either the CTH or a rat testis receptor radioligand assay. However, quantitatively, higher potency estimates were obtained with the CTH. The ability of LH preparations to displace radioiodinated pFSH or eFSH from CTH was generally very low with the notable exception of equine LH. The relative potency of highly purified eLH was approximately equal to that of the NIH-FSH-S16 standard (0.906 x NIH-FSH-S16) indicating that in the chicken, as in the rat, (Bousfield and Ward, Biochim. Biophys. Acta 885: 327, 1986), eLH has significant FSH activity. It is concluded that the chicken testis is a convenient and suitable source of FSH receptor (binding sites) for the bioassay of FSH, but that quantitative estimates of potency are not directly comparable when different sources of receptor are used. Finally the data show that eFSH has intriguing structural attributes which provide higher affinity to the chicken testis receptor than pFSH.

Animals↗
PubMed1990

FSH-induced expansion of the mouse cumulus oophorus in vitro is dependent upon a specific factor(s) secreted by the oocyte.

Although it has been shown that granulosa cells regulate the growth and meiotic maturation of mammalian oocytes, there is little evidence of a role for the oocyte in the differentiation or function of granulosa cells. To test the hypothesis that the oocyte participates in the regulation of granulosa cell function, oocytes were removed from isolated oocyte-cumulus cell complexes by a microsurgical procedure and oocytectomized complexes were tested for their ability to undergo expansion in response to follicle-stimulating hormone (FSH). FSH increased the levels of intracellular cAMP, the activity of the hyaluronic acid-synthesizing enzyme system, and induced cumulus expansion in intact complexes. In contrast, FSH did not induce increased hyaluronic acid-synthesizing enzyme activity or cumulus expansion in oocytectomized complexes. Therefore, the participation of the oocyte is necessary for the cumulus cells to synthesize hyaluronic acid and undergo cumulus expansion in vitro in response to stimulation with FSH. FSH induced the elevation of intracellular cAMP to the same extent in both intact and oocytectomized complexes and the cAMP analog 8-bromo cyclic adenosine monophosphate (8Br-cAMP) did not stimulate expansion in oocytectomized complexes. Therefore, the influence of the oocyte on cumulus expansion occurs downstream from the elevation of cAMP levels in the cumulus cells. Epidermal growth factor (EGF), a potent stimulator of cumulus expansion in intact complexes, which probably acts by a mechanism at least initially different from FSH, failed to stimulate cumulus expansion after oocytectomy. Next, oocytectomized complexes were either cocultured with germinal vesicle stage denuded oocytes or cultured in medium conditioned by denuded oocytes. In both cases, FSH or EGF stimulated expansion by oocytectomized complexes. The degree of expansion was directly correlated to the number of oocytes used to condition the medium. Contact between the oocyte and the cumulus cells is not necessary for cumulus expansion. Rather, a factor(s) secreted by the oocyte is necessary for the cumulus cells to undergo expansion in response to either FSH or EGF. FSH did not induce expansion of oocytectomized complexes in media conditioned by various somatic cells such as granulosa cells, fibroblasts, and Sertoli cells; by a mixed population of male germ cells; or by spermatozoa. This suggests that the expansion enabling activity is specific to the oocyte. These results demonstrate that the oocyte participates in the regulation of cumulus cell function.

Cells, Cultured↗
PubMed1989

Calcium-dependent stimulation of estrogen secretion by FSH from theca cells of the domestic hen (Gallus domesticus).

There is little information about the stimulation of estrogen secretion from theca cells of the domestic hen by follicle-stimulating hormone (FSH), and the mechanism of action of FSH through calcium has not been considered previously. The theca interna and externa cells from the third (F3) and fourth (F4) largest ovarian follicles of hens were separated, dispersed, and incubated in M199 with FSH (0.5 micrograms ml-1) or A23187 (0.1 or 1 microgram ml-1) with or without ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA) (2 mM) in calcium-replete or in calcium-free M199. Alternatively, androstenedione (10(-6) M) was added to the cells as aromatizable substrate, with or without FSH and/or EGTA. Estradiol and estrone secreted into the media during a 4-hr incubation period were measured by RIA. FSH stimulated estradiol and estrone secretion from all the cell preparations. The effect of FSH was abolished by the addition of EGTA or in calcium-free medium. A23187 stimulated estradiol and estrone secretion by the same extent as FSH, but did not do so in calcium-free medium. Androstenedione enhanced estradiol and estrone secretion, but estrogen secretion was further raised by the simultaneous addition of FSH. This action of FSH on aromatization was also abolished by EGTA. This evidence supports the hypothesis that calcium, possibly of extracellular origin, is an important mediator in the stimulation of aromatase systems in thecal cells of chickens.

Androstenedione↗
PubMed1984

Augmentation of aromatase activity by FSH in ovaries of fetal and neonatal mice in organ culture.

The stimulative effect of FSH on aromatase activity was investigated in ovaries of fetal (on days 17 and 18 of gestation) and neonatal mice (on days 0, 3, 6 and 9 after birth). Two to six ovaries, were cultured for 48 h in 2 ml of Medium 199 supplemented with insulin (5 micrograms/ml) and [1 alpha, 2 alpha, 6 alpha, 7 alpha, beta-3H]4-androstene-3,17-dione (0.35 microM) in the presence or absence of porcine FSH (0.5 units/ml) and the amount of [3H]oestradiol-17 beta and [3H]oestrone produced was estimated. In the presence of FSH, aromatase activity per ovary, which was found in all fetal and neonatal ovaries examined, increased with age. In the absence of FSH, however, the production of oestrogens could be demonstrated only in ovaries from 3- to 9-day old mice. FSH increased the aromatase activity by up to 10-fold. In spite of the stimulative effect of FSH on aromatase activity, FSH exerted no significant effect on DNA synthesis of the ovaries. The formation of primordial follicles could not be observed histologically in ovaries of fetal mice on day 17 of gestation, although the ovaries of 6- and 9-day old mice contained multilayered follicles. These results show that FSH stimulates the aromatase activity of the mouse ovary even before the formation of primordial follicles and that the stimulative effect of FSH on ovarian aromatase is not due to the proliferation of ovarian cells.

Androstenedione↗
PubMed1986

Paracrine control of Leydig cell activity by FSH dependent proteins from Sertoli cells: an in vitro study.

The regulating effect of follicle-stimulating hormone (FSH) on Leydig cell function was studied using a model of immature porcine Leydig and Sertoli cells cultured in a hormone supplemented defined medium. FSH pretreatment for 2 days of Leydig cells cultured alone was with no effect. FSH pretreatment of Leydig cells cocultured with Sertoli cells increases Leydig cell activity in an FSH dose-dependent manner with a maximal effect observed at 50 ng/ml porcine FSH (pFSH). Leydig cells cultured for 2 days in conditioned medium (CM) by FSH stimulated (FSH-CM) Sertoli cells, as compared to CM by unstimulated (control) (C-CM) Sertoli cells show an increase of their activity with a maximal effect observed at 50 ng/ml pFSH. Leydig cells cultured in CM as compared to non CM, show a marked development of organelles (smooth endoplasmic reticulum and mitochondria) involved in the steroidogenic activity. The activity of FSH-CM as compared to C-CM on Leydig cell function was non dialyzable and trypsin sensitive. These data suggest that Sertoli cells exert a regulatory action on Leydig cell steroidogenic activity via FSH dependent secreted proteins.

Animals↗
PubMed1983

Evidence for an FSH-releasing factor in the posterior portion of the rat median eminence.

To test the hypothesis that an FSH-releasing factor might be contained within the posterior portion of the median eminence (ME), the anterior half of the ME (aME) and the posterior half of the ME (pME) were removed separately from the brains of adult male rats and extracted in 0.2 N acetic acid. LH and FSH-releasing activities of the extracts were measured in vitro by incubating 8 hemipituitaries from adult male rats for 6 h at a dose of 5 tissue equivalents and determining the radioimmunoassayable LH and FSH released into the medium. LH release induced by the aME extracts was significantly greater than that induced by the pME in both experiments, whereas there were no differences in FSH release between aME and pME extracts. A significant dose-related increase in FSH release was noted in this system when 1 and 2 ng of synthetic LHRH were tested which indicates that the assay was sensitive to different amounts of LHRH with regard to FSH-releasing action. The content of immunoreactive LHRH in the extracts was almost twice as high in the aME as in the pME. Therefore, the results indicate that the pME has greater FSH-releasing activity than can be accounted for by its content of LHRH. The additional FSH-releasing activity is presumably due to an FSH-releasing factor distinct from LHRH.

Animals↗
PubMed1992

Developmental patterns of bioactive and immunoreactive FSH in the female rabbit: effects of ovariectomy.

A longitudinal study was performed to determine the relationship between immunoreactive and biologically active FSH in the serum of sham-operated and ovariectomized female rabbits. Twenty-two-day-old female rabbits, 8 per group, were sham-operated or bilaterally ovariectomized on day 23. Blood was taken every 3-4 days from each rabbit until they achieved a weight of 3 kg or age 100 days. Sera were analysed by radioimmunoassay for LH and FSH or for bioactive FSH. In sham-operated animals, immuno-FSH levels showed a 10-fold increase from 0.36 +/- 0.04 ng/ml to greater than 35 ng/ml between days 45 and 80. By contrast, bio-FSH levels increased more gradually from a baseline of 5.4 +/- 0.4 ng/ml to about 8 ng/ml. Bilateral ovariectomy resulted in a significant increase in both bio-FSH, 5.5 +/- 0.4 ng/ml to 12.6 +/- 1.5 ng/ml and immuno-FSH levels from 0.4 ng/ml to 5.2 +/- 1.4 ng/ml 24 h later. These levels of FSH remained elevated throughout the sampling period in both groups of animals and then decreased after day 100. Peripheral LH levels showed much more variation but were 2-fold higher in ovariectomized rabbits, 0.4-1.4 ng/ml in sham-operated vs. 0.8-2.4 ng/ml in ovariectomized rabbits. These results emphasize the marked variations in FSH levels according to the method of analysis. They also suggest that extra-ovarian factors may play a role in inhibiting gonadotropin release especially LH.

Aging↗