Gonadotropin Receptors and Regulation of Interstitial Cell Function in the Testis

Catt, Kevin J.; Dufau, Maria L.

doi:10.1016/b978-0-12-526303-0.50016-3

Cited by 25 publications

(8 citation statements)

References 148 publications

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“…These molecular weights are tentative and probably larger than the true values (for example, 18,000, 28,000, and 46,000 for a, :3 and af3, respectively) because of the abnormally low electrophoretic mobility caused by the high carbohydrate content of both subunits (>15% of their mass). The molecular weight of the photoaffinity-labeled components is probably less than 85,000 which is within the range 80,000-90,000 suggested by results of affinity column chromatography (2,3). DISCUSSION We have demonstrated that certain membrane components of granulosa cells can be photoaffinity-labeled with ABGG-125I-hCG and that these labeled complexes are resolved into three distinct bands by sodium dodecyl sulfate/polyacrylamide gel electrophoresis.…”

Section: Resultssupporting

confidence: 66%

“…It binds to specific surface receptors on ovary cells only as the a/ dimer. Such occupied receptors are thought to play a vital role in triggering a cascade of biological events (2). However, little is known about the chemical identity of the receptors and their association with other membrane components that may be involved in hormone action.…”

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confidence: 99%

“…However, little is known about the chemical identity of the receptors and their association with other membrane components that may be involved in hormone action. Results of affinity column chromatographic studies are not entirely clear; estimates of the molecular weight ranged from 190,000 to 80,000 (2,3).…”

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confidence: 99%

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Macromolecular photoaffinity labeling of the lutropin receptor on granulosa cells.

Ji¹,

Ji²

1980

Proc. Natl. Acad. Sci. U.S.A.

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Lutropin, a pituitary hormone, and human choriogonadotropin bind to the same receptors in the ovary and elicit identical responses. A photoactivable derivative of human choriogonadotro in was used to identify the lutropin receptor on porcine granuiosa cells. The hormone was condensed with a heterobifunctional reagent, the N-hydroxysuccinimide ester of 4-azidobenzoylglycylglycine, and iodinated. The 125I-labeled hormone ("2I-hormone) derivative associated with the same number of receptors as i25I-hormone itself did but with a slightly lower K., 2.98 X 109 M-1 compared with 5.1 X I09 M-' for 125I-hormone. The binding could be blocked with untreated hormone or lutropin but not with follitropin, prolactin, insulin, or bovine serum albumin. Its a and P subunits could be crosslinked to produce a, dimer by photolysis, the extent of crosslinking being dependent upon the reagent concentration used for the derivatization: 22.8% at 50 jiM, 37.3% at 100 jM, and 67.2% at 150 ;uM. When the 125I-hormone derivative bound to the cells was photolyzed for crosslinking and the products resolved by electrophoresis on sodium dodecyl sulfate/polyacrylamide gels un er reducing conditions, three new bands of lower electrophoretic mobility appeared in addition to a, ,6, and a bands. Formation of these crosslinked complexes required photolysis and the presence of both cells bearing the receptor and the '25I-hormone derivative. It could be blocked by excess untreated hormone. The three bands correspond to molecular weights, 96,000 4 6,700, 66,000 ± 4,600, and 63,000 : 4,400. Because the hormone has a high carbohydrate content and such glycoproteins are known to exhibit anomalous electrophoretic mobilities, these estimates must be tentative. Lutropin, a glycoprotein hormone composed of two dissimilar subunits, a (18,000 daltons) and 3 (16,000 daltons), is involved in the regulation of the endocrine and reproductive functions of the gonads (1). It binds to specific surface receptors on ovary cells only as the a/ dimer. Such occupied receptors are thought to play a vital role in triggering a cascade of biological events (2). However, little is known about the chemical identity of the receptors and their association with other membrane components that may be involved in hormone action. Results of affinity column chromatographic studies are not entirely clear; estimates of the molecular weight ranged from 190,000 to 80,000 (2, 3).Several years ago, macromolecular photoaffinity labeling of surface receptors for polypeptide ligands was developed (4-6). This technique, an alternative to affinity column chromatography, uses photoactivable heterobifunctional reagents. Polypeptide ligands coupled with such reagents under physiological conditions are allowed to bind to their specific receptors which are then crosslinked. Recently it was reported that the 2-nitro-4-azidophenyl derivative of ovine lutropin failed toThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "ad...

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Section: Resultssupporting

confidence: 66%

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confidence: 99%

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Macromolecular photoaffinity labeling of the lutropin receptor on granulosa cells.

Ji¹,

Ji²

1980

Proc. Natl. Acad. Sci. U.S.A.

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“…The hLH receptor differs from rat testis and ovarian receptor, which lack species specificity for LH-like gonadotropins (17). Only hLH among the pituitary hormones studied displaced the binding of radiolabeled hCG from the receptor.…”

Section: Discussionmentioning

confidence: 81%

Luteinizing Hormone Receptors in Human Ovarian Follicles and Corpora Lutea during Menstrual Cycle and Pregnancy*

Rajaniemi

Rönnberg

Kauppila

et al. 1981

The Journal of Clinical Endocrinology & Metabolism

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Specific high affinity, low capacity binding of [ l25 I]iodo-hCG was demonstrated in homogenates of isolated granulosa cells and corpora lutea of human ovary throughout the menstrual cycle and pregnancy. The binding of radiolabeled hCG to the receptor was time, temperature, ion concentration, and pH dependent. The treatment of ovarian membrane particles with trypsin decreased binding by about 75%, whereas treatment and neuraminidase resulted in a 400% increase in binding. These results suggest a protein nature of the receptor and that a portion of the receptors may be masked in the membrane by sialic acid. The receptor displayed high specificity for hCG and human LH, indicating that they share the same receptor site in the human ovary. The receptor bound hCG with high affinity. The apparent equilibrium association constant for hCG was 2.2 X 10 9 M~\ The receptor concentration increased from the early follicular phase to ovulation by about 1.6-fold. After an apparent transient fall associated with the ovulatory period, the receptor concentration increased further by about 4-fold by day 17 of the cycle and thereafter remained virutally unchanged until the end of the cycle. Homogenates of corpora lutea obtained during the follicuar phase aso bound specifically radiolabeled hCG, suggesting that the regression of the corpora lutea is not primarily due to the loss of receptors for human LH. The receptor concentration measured in corpora lutea of early pregnancy was clearly lower than that in corpora lutea of the menstrual cycle. This is most likely due to occupation and downregulation of the receptors by high serum hCG. The number of receptors in corpora lutea tended to increase towards the end of pregnancy.Our results indicate that the maturation and subsequent luteinization of human ovarian follicles is associated with a biphasis increase in the number of LH (hCG) receptors in granulosa cells. The changes in the concentration of available receptor may have a determining role in the regulation of follicular and corpus luteum development and function. (J Clin Endocrinol Metab 108: 307, 1981) H UMAN LH (hLH) and hCG appear to be the major luteotropic factors for the human corpus luteum during the menstrual cycle and pregnancy (1-4). Specific stimulation of steroidogenesis in human corpora lutea by hLH and hCG has been demonstrated in vitro (1, 2, 5). In addition, the administration of hCG in vivo during the early luteal phase prolongs the lifespan and function of the corpus luteum to a certain extent, but not beyond 9 days (3, 4). Other data have shown that hLH can also extend the lifespan of the corpus luteum of the menstrual cycle and increase the serum progesterone concentration (3, 4). Fundamental to our understanding of regulation of follicular development and corpus luteum function is knowledge of the properties of the gonadotropin recep-

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“…However, in all of these tissues cAMP is thought to be the primary intracellular regulator of hormone production. cAMP levels rapidly increase when ACTH or gonadotropins act upon the adrenal cortex or gonads, respectively, and cAMP analogues are potent stimulators of steroid hormone production by these tissues (23). The bovine placenta appears to differ from these other steroidogenic tissues and may resemble the zona glomerulosa of the adrenal cortex, a tissue in which calcium rather than cyclic nucleotides seems to be the primary intracellular signal increasing aldosterone synthesis (24)(25)(26).…”

Section: Methodsmentioning

confidence: 99%

Calcium-dependent, cyclic nucleotide-independent steroidogenesis in the bovine placenta.

Shemesh¹,

Hansel²,

Strauss³

1984

Proc. Natl. Acad. Sci. U.S.A.

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Dispersed bovine placental cells (fetal cotyledon and maternal caruncle) were shown to synthesize progesterone. To determine if their steroidogenic activity could be modulated by a cyclic nucleotide-mediated process, we added luteinizing hormone, 8-bromoadenosine 3',5'-monophosphate, 8-bromoguanosine 3',5'-monophosphate, adenosine, or cholera toxin to dispersed cells from placentomes of 100-283 days gestational age and examined progesterone synthesis during 3-to 16-hr incubation periods. Net progesterone production, defined as the amount of progesterone released in excess of the zero-time cellular progesterone content, was determined by using a specific RIA. None of these agents significantly affected progesterone synthesis. In contrast, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (MIX; 0.2-0.5 mM) caused a marked increase in progesterone formation. In time course studies it was found that MIX produced a 5-fold increase in progesterone production in 16 hr, with steroid production increasing linearly during this time. MIX also increased the conversion of exogenous pregnenolone to progesterone by placental cells. In view of the failure of cyclic nucleotide analogues and activators of adenylate cyclase to stimulate steroidogenesis, it was necessary to consider other modes of action of MIX. Since MIX is known to affect intracellular calcium translocation, we examined the effects of the calcium ionophore A23187 on progesterone formation. This drug enhanced progesterone formation and augmented the stimulatory effects of MIX. The stimulatory action of A23187 was not affected by cyclic nucleotide analogues. Our data suggest that progesterone synthesis in the bovine placentome is calcium dependent and cyclic nucleotide independent.The bovine placenta has been generally disregarded as a site of progesterone synthesis (1-4). However, conversion of [3H]pregnenolone to radioactive progesterone by bovine placental preparations has been demonstrated (5), and our previous studies indicated that enzyme-dispersed bovine placentomes are capable of producing progesterone in culture (6). The present study was conducted to further define the endocrine activity of the bovine placentome with respect to progesterone production and to elucidate mechanisms by which placental steroidogenesis is controlled. The data presented suggest that calcium is the key mediator of placental steroid hormone synthesis, in contrast to other steroidogenic glands in which cyclic nucleotides modulate hormone formation. Assay of Progesterone. Progesterone secreted into the incubation medium was quantified in diethyl ether extracts by RIA, as described (8). The inter-and intraassay coefficients of variation of the progesterone assay were 11% and 9%, respectively. In all cases, net progesterone secretion into the medium was determined by subtracting progesterone levels in the cells and incubation medium at zero time from levels after the indicated incubation periods. The antibody displayed negligible (<1%) cross-reactivity with pregnenol...

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Gonadotropin Receptors and Regulation of Interstitial Cell Function in the Testis

Cited by 25 publications

References 148 publications

Macromolecular photoaffinity labeling of the lutropin receptor on granulosa cells.

Macromolecular photoaffinity labeling of the lutropin receptor on granulosa cells.

Luteinizing Hormone Receptors in Human Ovarian Follicles and Corpora Lutea during Menstrual Cycle and Pregnancy*

Calcium-dependent, cyclic nucleotide-independent steroidogenesis in the bovine placenta.

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