Stimulatory Effect Of FSH Research Articles

Differential effects of follicle-stimulating and luteinizing hormones on testosterone production by mouse testes

In adult mice, direct intratesticular injection of ovine follicle-stimulating hormone (o-FSH-13; AFP2846-C, from NIAMDD, < 1% LH contamination) at 10, 100 or 1000ng significantly elevated concentrations of testosterone (T) within the testis. These effects were rapid, with peak values attained by 15 min, and transient, with return to values comparable to that in the contralateral, saline-injected testis within 90 min. Intratesticular injection of FSH (1 μg) significantly increased testicular T levels in 15- and 60-day old mice. This contrasted with the effects of intratesticular administration of human chorionic gonadotropin (hCG), which stimulated T production significantly at 30 days of age through adulthood. In adult mice, the equivalent LH to the possible contamination in the FSH preparation (1 ng) had no effect. Intratesticular injection of 10 ng LH produced comparable stimulation to that by 100 ng FSH (~7-fold). Systemic pre-treatment with a charcoal-treated porcine follicular fluid (PFF) extract for 2 days reduced plasma FSH levels [86 ± 17 (5) vs 700 ± 8 (6); P < 0.05], but had no effect on plasma LH. Twenty-four hours after the last treatment, the response to intratesticular injection of hCG (2.5 mIU), FSH (100ng) or LH (10 ng) was also significantly attenuated in these mice. Intratesticular injection of PFF had no direct effect on testicular T levels. In vitro T production in the presence of hCG, LH or FSH were differentially affected by the concentrations of calcium (Ca 2+) or magnesium (Mg 2+) in the incubation media. The stimulatory effects of FSH were apparent at significantly lower levels of Ca 2+ or Mg 2+, than were those of LH or hCG. The results of these studies indicate that FSH is capable of stimulating testicular T production. Furthermore, the responsiveness to FSH is qualitatively different than that to LH/hCG in terms of the age pattern, as well as the dependence on Ca 2+ or Mg 2+. In addition, plasma FSH levels appear to influence testicular responsiveness to direct exogenous administration of gonadotropins. These studies indicate that FSH stimulation of T production can be differentiated from those of LH, and that these effects of FSH can be observed under physiological conditions.

Use of antisera to follicle-stimulating hormone (FSH) to detect non-FSH factors in human serum which modulate rat granulosa cell steroidogenesis.

We measured the ability of serum from women to stimulate steroidogenesis in cultured granulosa cells. Serum promoted estradiol and progesterone synthesis in proportion to its FHS content measured by RIA [i.e. serum from postmenopausal women (PM) greater than serum from the midcycle at the time of the gonadotropin surge (MC) greater than serum from the first day of the menstrual cycle (D1) greater than serum from a hypophysectomized woman (AP)]. The FSH activity of these sera was reduced but not eliminated when we included excess antisera to ovine or human FSH in the culture medium (i.e. PM greater than MC greater than D1 greater than AP). These antisera completely neutralized the actions of ovine FSH, human FSH, and menopausal gonadotropin (Pergonal) added to serum. In contrast to the stimulation seen with 5% or lower concentrations of serum in the culture medium, we observed that 10-20% serum inhibited FSH-induced androgen aromatization and progesterone accumulation. The degree of stimulation or inhibition of steroidogenesis depended on the number of granulosa cells added to each culture. High initial cell concentrations inhibited the ability of the cells to respond to either serum or PMSG. In addition to factors which stimulate or inhibit FSH-induced steroidogenesis, human serum contains factors distinct from FSH which cause the cells to flatten and adhere more tightly to the culture dishes. Although progesterone synthesis was increased in cells which had flattened on the surface of the culture dishes, this phenomenon was not a prerequisite for serum-induced steroidogenesis. We conclude that serum contains factors immunologically distinct from FSH, possibly of pituitary origin, which induce granulosa cell steroidogenesis. In addition, serum contains inhibitory substances which block hormone-induced steroidogenesis and which tend to obscure the stimulatory effects of FSH. Detection of both factors depends in part on the number of granulosa cells used to innoculate the cell cultures.

Amino acid uptake and protein synthesis in rat testes: stimulation by dissociable factors.

Low concentration (25 mM) of sodium in the incubation medium produced a decrease in the amino acid uptake by the testis tissue as well as a reduction in the response to FSH. In this experimental condition, the basal protein synthesis and the stimulatory effect of FSH was not modified. The subcutaneous administration of testosterone to 15 day old rats increased the protein synthesis in the testis without any modification in the amino acid uptake. The addition of DBcAMP (1 mM) or glucose (14 mM) to the incubation medium increased the protein synthesis in the testes of immature (12 day-old) or prepubertal (32 day-old) rats respectively. The amino acid uptake was not modified. In immature rat testes, with protein synthesis completely inhibited by cycloheximide, the restoration of the sodium concentration in the incubation medium to normal levels produced an increase in amino acid uptake. The results above seem to indicate that protein synthesis and amino acid uptake in rat testes tissue can be regulated, at least partially, by different factors.

Interactions between immature porcine Leydig and Sertoli cells in vitro. An ultrastructural and biochemical study.

Interactions between Leydig and Sertoli cells, as well as a stimulatory effect of FSH on Leydig cell activity, have been reported in many studies. In order to investigate these interactions, the ultrastructure of immature pig Leydig cells under different culture conditions has been studied. When cultured alone in a chemically defined medium, there is a marked regression of the Leydig cell smooth endoplasmic reticulum and a swelling of the mitochondria. Addition of FSH or hCG does not prevent these phenomena. Co-culturing of Leydig cells with Sertoli cells from the same animal maintains the smooth endoplasmic reticulum at the level seen in vivo and in freshly isolated Leydig cells. The addition of FSH to the co-culture stimulates its development and increases Leydig cell activity, as assessed by an increase in hCG binding sites and an increased steroidogenic response to hCG. These results suggest that Sertoli cells exert a trophic effect on Leydig cells, and that the stimulatory effect of FSH on Leydig cell function is mediated via the Sertoli cells. These results reinforce the concept of a local regulatory control of Leydig cell steroidogenesis.

Developmental changes in the hormonal regulation of rat testis Sertoli cell adenylyl cyclase.

The stimulatory effects of FSH on Sertoli cell functions such as cAMP accumulation, protein kinase activation, and RNA and protein synthesis wane during testis maturation. However, FSH receptors increase with age and addition of cAMP stimulates these biochemical events in Sertoli cells from animals of any age. In order to determine if this loss of responsiveness to FSH was due to an inability to stimulate adenylyl cyclase, the hormonal responsiveness of this enzyme was investigated as a function of testicular development. In agreement with intact cell studies, adenylyl cyclase activity was found to be stimulated by FSH 2- to 3-fold in homogenates of testes from immature (5-20 days of age) Sertoli cell-enriched rats, while no stimulation of the enzyme by FSH was observed in similar homogenates from Sertoli cell-enriched animals 20 days of age or older. The possibility of a decrease in enzyme sensitivity to the gonadotropin as a function of maturation ws ruled out by dose-response studies. Catalytic activity of the enzyme was retained with increasing animal age as evidenced by the ability of fluoride (10 mM) to stimulate basal activity 4-fold. Hormonal responsiveness of the Sertoli cell adenylyl cyclase of mature animals could be restored, however, either by addition of the nonmetabolizable guanosine 5'-triphosphate analog, 5'-guanylyl-imidodiphosphate to homogenates or by preparation of membrane particles. We found that 5'-guanylyl-imidodiphosphate selectively potentiated FSH effects on cyclase in testicular homogenates from mature animals while having no effect on the relative degree of hormone stimulation in homogenates from immature animals, and that in contrast to homogenates, testicular membrane preparations retain their FSH responsiveness upon animal maturation.

Regulation of protein kinase inhibitor by follicle-stimulating hormone in Sertoli cells in vitro.

The heat-stable protein inhibitor of cAMP-dependent protein kinase is specifically regulated by hormones in cultures of rat Sertoli cells maintained under completely defined conditions. Hormones that are known to elevate Sertoli cell cAMP concentrations, namely FSH and isoproterenol, produce a 4- to 5-fold increase in the specific activity of protein kinase inhibitor, whereas testosterone and LH have no effect. The stimulatory effects of FSH or isoproterenol on protein kinase inhibitor are completely mimicked by dibutyryl cAMP. The ability of FSH to stimulate protein kinase inhibitor is dependent upon the age of the animals used as a source for the Sertoli cells. FSH stimulates protein kinase inhibitor activity in cells from 9- and 16-day-old animals, but not in cells from 32-day-old animals. On the other hand, isoproterenol or dibutyryl cAMP will stimulate protein kinase inhibitor in cells from both young and old animals. FSH can stimulate protein kinase inhibitor activity in older cells only in the added presence of the phosphodiesterase inhibitor, 1-methyl-3-isobutyl xanthine. Using specific antibodies to protein kinase inhibitor, we have shown that this protein is regulated by hormones via preferential stimulation of de novo synthesis of the inhibitor. (Endocrinology 108: 427, 1981)

Possible influence of gonadotrophins on formation in vivo of pyridoxal phosphate.

FSH administered to normal rats increased the activity of pyridoxine phosphate oxidase of both liver and kidney and, consequently, pyridoxal phosphate levels in these tissues were elevated. LH administration, on the other hand, decreased the activity of pyridoxine phosphate oxidase, resulting in diminished pyridoxal phosphate level in the tissues. The stimulatory effect of FSH on the activity of liver and kidney pyridoxine phosphate oxidase was not observed in castrated-adrenalectomised rats unless supplemented with cortisone and testosterone, respectively. Puromycin treatment prevented the FSH-induced rise in the activity of liver and kidney pyridoxine phosphate oxidases. It is suggested that FSH stimulates the activity of liver and kidney pyridoxine phosphate oxidase by increasing the synthesis of apoproteins of the enzyme, and the effect of FSH on liver is dependent on the presence of adrenal corticoids while the presence of testosterone is a prerequisite for the FSH to have its effect on kidney pyridoxine phosphate oxidase.

An LHRH agonist inhibits FSH-induced cyclic AMP accumulation and steroidogenesis in porcine granulosa cells in culture

The direct action of a potent LHRH agonist, [D-Ser-(TBU) 6, des-Gly-NH 2 10]LHRH ethylamide was studied in porcine granulosa cells in primary culture. The LHRH agonist inhibits by 30 to 55% the stimulatory effect of FSH on cyclic AMP accumulation up to 9 hours of incubation. In the absence of FSH, a more transient inhibitory effect is observed on cyclic AMP levels. The LHRH agonist inhibits both basal and FSH-induced progesterone secretion. The present data suggest that ovarian LHRH receptors are negatively coupled to adenylate cyclase.

Effect of Follicle-Stimulating Hormone and Its Antiserum on the Activity of Ornithine Decarboxylase in the Ovary of Rat and Hamster*

The ability of FSH to stimulate the activity of ornithine decarboxylase (ODC) in the ovary of the immature rat and cycling hamster has been examined using specific antisera to gonadotropins. The stimulatory effect of FSH on ODC activity in the ovary of the immature rat was abolished when LH antiserum was administered along with FSH, while similar administration of FSH antiserum had no effect on LH action in stimulating ODC activity, thereby demonstrating the specificity of the LH effect. During the estrus cycle of the hamster, ODC activity in the ovary could be detected only on the evening of proestrus, the maximal activity seen at 1700 h being associated with both the Graafian follicles and the rest of the ovarian tissue. Neutralization of the proestrous FSH surge had no effect on the activity of ODC in either of these tissues, while similar administration of LH antiserum at 1300 h of proestrus completely inhibited the ODC activity in both large follicles and the rest of the ovarian tissue. Thus, the surge of LH, but not of FSH, appears to be responsible for regulating the ODC activity in the ovary of the cycling hamster.

Steroidogenesis by enzyme-dispersed turtle ( Chrysemys picta) ovarian cells in response to ovine gonadotropins (FSH and LH)

Follicular cells obtained by collagenase dispersion of turtle ( Chrysemys picta) ovarian tissue at three different times of the year (summer, stage 1; fall, stage 2; spring, stage 3) were examined for steroid (progesterone, testosterone, estradiol) secretion in response to increasing concentrations of ovine FSH and LH. At all three stages of the cycle FSH stimulated steroid production. Although both progesterone and testosterone were secreted by cells obtained from ovaries at stages 1 and 2 of the cycle, estradiol could not be detected in incubations of cells at these times. However, at stage 3 of the cycle, a stimulatory effect of FSH on estradiol production was apparent. The slight stimulatory effect of high doses of LH on progesterone and testosterone production may be due to FSH contamination in this particular NIH preparation. Turtle luteal cells prepared by the same method secreted progesterone in response to dibutyryl cyclic AMP.