scholarly journals Role of FSH, numbers of FSH receptors and testosterone in the regulation of inhibin secretion during the seasonal testicular cycle of adult rams

Reproduction ◽  
2002 ◽  
pp. 269-280 ◽  
Author(s):  
LM Sanford ◽  
CA Price ◽  
DG Leggee ◽  
SJ Baker ◽  
TA Yarney
Keyword(s):  
Breeding Season ◽  
Sertoli Cells ◽  
Fsh Receptor ◽  
Relative Importance ◽  
Testosterone Secretion ◽  
Receptor Mrna ◽  
Testicular Recrudescence ◽  
Natural Photoperiod ◽  
Stimulation Of

The regulation of inhibin secretion has not been elucidated fully in male ruminants. The aim of this study was to determine the relative importance of FSH and testosterone concentrations, and FSH receptors, in the control of secretion of immunoactive inhibin in rams. In Expt 1, temporal changes in hormone concentrations and testicular FSH binding were determined for two groups of rams (n = 4) kept under opposite, alternating 4 month periods of long (16 h light:8 h dark) and short (8 h light:16 h dark) days. Testicular biopsies (1-2 g) were collected when the testes were regressed, redeveloping, redeveloped and regressing. In Expt 2, separate groups of rams (n = 4) kept under natural photoperiod (latitude 45 degrees 48 minutes N) were designated as controls or passively immunized (for 3 weeks) with sufficient oestradiol antiserum to increase testosterone secretion without altering LH and FSH; this was done when the testes were regressed (non-breeding season) and redeveloped (breeding season). In both groups of rams (Expt 1), 'seasonal' increases in FSH concentrations began a few weeks earlier than did increases in inhibin concentrations. FSH reached maximum concentrations during testicular recrudescence, whereas numbers of FSH receptors in the testis and circulatory inhibin concentrations did not reach peak values until the testes were fully developed. Numbers of FSH receptors per testis, but not FSH concentration, were positively correlated (r = 0.65) with inhibin concentrations across the four stages of the testicular cycle. Near the end of testicular recrudescence early in the breeding season (Expt 2), relatively high FSH concentration was associated with increased abundance of FSH receptor mRNA (90%) and number of receptors (45%) in the testis and increased inhibin concentrations (50%), compared with when the testes were regressed. Moderate, physiological increases in testosterone secretion in immunized rams did not affect inhibin in either season. These results indicate that: (i) FSH stimulation of immunoactive inhibin secretion by Sertoli cells as testes recrudesce is via increases in secretion (early) and cognate receptors (late); (ii) FSH upregulates the synthesis of its own receptor late in recrudescence; and (iii) the positive correlation (r = 0.70) observed between circulatory testosterone and immunoactive inhibin does not reflect a causal relationship.

scholarly journals Follicle-Stimulating Hormone (FSH) Transiently Blocks FSH Receptor Transcription by Increasing Inhibitor of Deoxyribonucleic Acid Binding/Differentiation-2 and Decreasing Upstream Stimulatory Factor Expression in Rat Sertoli Cells

Endocrinology ◽  
2009 ◽  
Vol 150 (8) ◽  
pp. 3783-3791 ◽  
Author(s):  
Pushpa Viswanathan ◽  
Michelle A. Wood ◽  
William H. Walker
Keyword(s):  
Protein Binding ◽  
Sertoli Cells ◽  
Fsh Receptor ◽  
Upstream Stimulatory Factor ◽  
Binding Studies ◽  
Nuclear Extracts ◽  
E Box ◽  
Stimulatory Factor ◽  
Stimulation Of

FSH acts through the FSH receptor (FSHR) to modulate cell processes that are required to support developing spermatozoa. Within the testis, only Sertoli cells possess receptors for FSH and are the major targets for this regulator of spermatogenesis. FSH stimulation of Sertoli cells for 24–48 h is known to induce Fshr mRNA expression through an E-box motif (CACGTG) located 25 bp upstream of the transcription start site. In contrast, FSH stimulation for 8 h inhibits Fshr transcription. DNA-protein binding studies performed using nuclear extracts from Sertoli cells show that protein binding to the Fshr promoter E-box was reduced 68% after 6 h of FSH stimulation but increased 191% over basal levels after 48 h of stimulation. The proteins binding to the Fshr E-box were identified as upstream stimulatory factor (USF)-1 and -2. FSH stimulation transiently decreased USF1 levels and increased the expression of the inhibitor of DNA binding/differentiation (ID)-2 repressor protein with the same kinetics as the decreased USF/E-box interactions. Overexpression of ID2 resulted in a dose-dependent decrease in USF-driven Fshr promoter activity in the MSC-1 Sertoli cell line, and ID2 inhibited USF binding to the Fshr E-box. Together, these studies suggest that stimulation of Sertoli cells with FSH transiently decreases expression of the USF1 activator and induces accumulation of the ID2 repressor, to block USF binding to the Fshr promoter and delay activation of Fshr transcription. This FSH-regulated mechanism may explain the cyclical changes in Fshr expression that occurs in Sertoli cells in vivo.

scholarly journals Regulation of rat Sertoli cell function by FSH: possible role of phosphatidylinositol 3-kinase/protein kinase B pathway

2002 ◽  
Vol 174 (2) ◽  
pp. 195-204 ◽  
Author(s):  
SB Meroni ◽  
MF Riera ◽  
EH Pellizzari ◽  
SB Cigorraga
Keyword(s):  
Protein Kinase ◽  
Sertoli Cell ◽  
Mechanism Of Action ◽  
Sertoli Cells ◽  
Cell Function ◽  
Protein Kinase B ◽  
Lactate Production ◽  
Phosphatidylinositol 3 Kinase ◽  
Stimulation Of

The FSH molecular mechanism of action is best recognized for its stimulation of the adenylyl cyclase/cAMP pathway via activation of a G protein. Recently, links between cAMP, phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB) signaling pathways in thyroid and granulosa cells have been observed. The aim of this study was to investigate the possible role of the PI3K/PKB pathway in FSH regulation of Sertoli cell function. Twenty-day-old rat Sertoli cell cultures were used. An increase in phosphorylated PKB (P-PKB) levels in response to FSH and dibutyryl-cAMP was observed. These increments in P-PKB levels were not observed in the presence of two PI3K inhibitors, wortmannin and Ly 294002. Inhibition of protein kinase A (PKA) by H89 did not decrease FSH stimulation of P-PKB levels. Taken together, these results indicate that FSH increases P-PKB levels in a PI3K-dependent and PKA-independent manner in rat Sertoli cells. In addition, wortmannin partially inhibited the ability of FSH to stimulate two well-known parameters of Sertoli cell function - transferrin secretion and lactate production - at doses equal to or lower than 0.1 microM. Related to lactate production, a decrease in FSH stimulation of lactate dehydrogenase activity and of basal and FSH-stimulated glucose uptake was observed in the presence of wortmannin. These metabolic changes were in most cases accompanied by changes in the levels of P-PKB. Altogether, these results suggest a meaningful role of the PI3K/PKB pathway in the mechanism of action of FSH in rat Sertoli cells.

INDUCTION OF OVULATION IN SHEEP BY ELECTRICAL STIMULATION OF HYPOTHALAMIC REGIONS

1970 ◽  
Vol 46 (3) ◽  
pp. 305-311 ◽  
Author(s):  
F. PRZEKOP ◽  
E. DOMAŃSKI
Keyword(s):  
Electrical Stimulation ◽  
Breeding Season ◽  
Anterior Hypothalamus ◽  
Oestrous Cycle ◽  
Induction Of Ovulation ◽  
Gonadotrophin Secretion ◽  
Hypothalamic Nuclei ◽  
Medial Hypothalamus ◽  
Stimulation Of

SUMMARY Electrical stimulation of the anterior hypothalamus (regions of the supraoptic and anterior hypothalamic nuclei) or of the ventro-medial hypothalamus (infundibular or ventro-medial nuclei) during the last month of anoestrus in ewes induced ovulation within 72 hr., while similar stimulation of the same centres during the breeding season on the 12th day of the oestrous cycle did not advance ovulation. The role of the hypothalamic centres in the control of gonadotrophin secretion and ovulation is discussed in the light of these results.

scholarly journals A Review of the Physiopathological Role of Follicle Stimulating Hormone (FSH) in Reproduction and in Vascularization of Tumors

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
O. N Nwankudu
Keyword(s):  
Sertoli Cells ◽  
Anterior Pituitary ◽  
Ovarian Follicle ◽  
Follicle Stimulating Hormone ◽  
Gonadotropin Releasing Hormone ◽  
Thecal Cells ◽  
Androgen Binding ◽  
Stimulation Of ◽  
Stimulating Hormone

Follicle Stimulating Hormone (FSH) is a polypeptide hormone secreted by the cells of the anterior pituitary whose primary function is stimulation of ovarian follicle to grow and mature in females. Additionally, FSH stimulates the granulosa cells in the ovarian follicle to synthesize aromatase which converts androgen produced by the thecal cells to estradiol. Estradiol in the blood primes the hypothalamus to produce stronger pulses of Gonadotropin Releasing Hormone (GnRH) leading to secretion of Luteinizing hormone (LH). Then, LH causes ovulation and the developmentof corpus luteum. But, in the males, FSH stimulates the Sertoli cells to secret Androgen Binding Protein (ABP) which concentrates local testosterone leading to stimulation of spermatogenesis. However, FSH has been identified in many angiogenic vasculature of many tumors. The review tries to bring out FSH in reproduction and pathology as well as reveal certain solutions which may be useful in infertility and oncogenic therapy.

Follicle-stimulating hormone-dependent estrogen secretion by rat Sertoli cells in vitro: Modulation by calcium

1991 ◽  
Vol 125 (3) ◽  
pp. 280-285 ◽  
Author(s):  
J. Alan Talbot ◽  
Ann Lambert ◽  
Robert Mitchell ◽  
Marek Grabinski ◽  
David C. Anderson ◽  
...  
Keyword(s):  
Sertoli Cells ◽  
Culture Medium ◽  
Follicle Stimulating Hormone ◽  
Dibutyryl Camp ◽  
Immature Rat ◽  
Estradiol Secretion ◽  
Old Rats ◽  
Stimulating Hormone

Abstract We have investigated the role of Ca2+ in the control of FSH-induced estradiol secretion by Sertoli cells isolated from 8-10 days old rats. Exogenous Ca2+ (4-8 mmol/1) inhibited FSH-stimulated E2 secretion such that, with 8 mmol/l Ca2+ and FSH (8 IU/l) E2 secretion decreased from 2091±322 to 1480±84 pmol/l (p<0.002), whilst chelation of Ca2+ in the culture medium with EGTA (3 mmol/l) increased E2 secretion from 360±45 to 1242±133 pmol/l) in the absence of FSH. Further, EGTA (3 mmol/l) markedly potentiated FSH (8 IU/l), forskolin (1 μmol/l) and dibutyryl cAMP (1 mmol/l)-stimulated E2 secretion. Addition of the Ca2+ ionophores, ionomycin (2-5 μmol/l) and A23187 (2 μmol/l), inhibited FSH (8 IU/l)-stimulated E2 secretion by >80%. The effect of ionomycin was totally reversible, whereas that of A23187 was irreversible. Ionomycin (5 μmol/l) had no effect on EGTA-induced E2 secretion in the absence of FSH, but reduced EGTA-provoked E2 secretion by 59% in the presence of FSH (8 IU/l). Similarly, forskolin- and dibutyryl cAMP-provoked E2 production was inhibited 46-50% by ionomycin (5 μmol/l). We conclude that FSH-induced E2 secretion from immature rat Sertoli cells is modulated by intra- and extracellular Ca2+.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

Population Control (Review Article)

1961 ◽  
Vol 1 (3) ◽  
pp. 89-98
Author(s):  
Karol J. Krotki
Keyword(s):  
Population Control ◽  
Review Article ◽  
Small Enterprise ◽  
Opportunity Costs ◽  
Relative Importance ◽  
Factual Information ◽  
Undue Influence ◽  
Clear Cut ◽  
Economic Considerations

Discussions about the role of small enterprise in economic development tend to remain inconclusive partly because of the difficulty of assessing the relative importance of economic and non-economic objectives and partly because of the dearth of factual information on which to base an economic calculus. It is probably true, moreover, that, because of a lack of general agreement as to the economic case for or against small enterprise, non-economic considerations, including some merely romantic attitudes toward smallness and bigness, tend to exert an undue influence on public policies. There may, of course, be no clear-cut economic case. And noneconomic considerations should and will inevitably weigh significantly in policy decisions. If, however, some of the economic questions could be settled by more and better knowledge, these decisions could more accurately reflect the opportunity costs of pursuing non-economic objectives.

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