Temporal Relationship Between hCG Induced Desensitization of LH/hCG Responsive Adenylyl Cyclase and Down regulation of LH/hCG Receptors in the Rat Testis

Jahnsen, Tore; Purvis, K.; Torjesen, Peter A.; Hansson, V.

doi:10.3109/01485018108987356

Cited by 21 publications

(6 citation statements)

References 25 publications

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“…In the human testes, duration of the significant reduction was 5 days in vivo and in vitro. The findings in the rat testes were almost consistent with other previous reports [2,4,6]. As for humans, there have been only a few reports [3,5] referring to the changes in testicular LH/hCG receptors after hCG treat ment: Sharpe et al [3] showed lower hCG binding in hCG-treated infertile men a day after the treatment (1,000-4,000 IU hCG) than in untreated infertile men, while Lackgren et al [5] found that 1-4 days after hCG treatment (500-1,000 111 hCG) an increase in specific LH binding was caused in biopsied testes taken from cryptorchid boys.…”

Section: Discussionsupporting

confidence: 82%

“…In the rat testes, significant reductions in the specific hCG binding sites continued for 7 days after the expo sure to hCG in organ culture as well as after the admin istration of hCG in vivo [the data of in vivo experiments performed in the present study are omitted, because the results only confirm the work published by other labora tories, see 2,4,6]. In the human testes, duration of the significant reduction was 5 days in vivo and in vitro.…”

Section: Discussionsupporting

confidence: 41%

“…In the testes the contents of luteinizing hormone (LH)/human chorionic gonadotro pin (hCG) binding sites have been shown to change fol lowing the administration of hCG [1][2][3][4][5][6][7]. However, such studies have been mainly confined to laboratory animals [1,2,4,6,7], and there have been only a few reports on this change in humans [3,5]. In addition, the mechanism by which hCG exerts an effect on its own binding sites is still unclear.…”

Section: Introductionmentioning

confidence: 96%

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Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in vivo and in vitro

Namiki¹,

Kitamura²,

Nonomura³

et al. 1988

Horm Res

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Changes in rat and human testicular human chorionic gonadotropin (hCG) binding sites induced by hCG were estimated in vivo and in vitro. After a single administration of hCG, the specific ¹²⁵I-hCG bindings were significantly reduced for 7 and 5 days in rat and human testes, respectively. Thereafter, ¹²⁵I-hCG bindings had recovered to pretreatment values by the 14th day after the administration. Occupied hCG bindings accounted for about half of the reduced bindings on the day after administration of hCG. After this time, however, the occupancy did not contribute so much to the reduction of the bindings. In experiments in vitro using the organ culture technique, an exposure to hCG for 24 h induced a dose-related significant loss of the specific ¹²⁵I-hCG bindings for 7 and 5 days in rat and human testes, respectively. Thereafter, the loss was gradually recovered. These patterns of changes in ¹²⁵I-hCG bindings in vitro were similar to those in vivo. These findings suggest that the reduction in hCG binding sites by hCG is due to not only occupancy but also downregulation of the binding sites and that the testicular organ culture method used in the present study is useful to study hormonal regulation of testicular function, especially in human testes.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionsupporting

confidence: 41%

Section: Introductionmentioning

confidence: 96%

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Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in vivo and in vitro

Namiki¹,

Kitamura²,

Nonomura³

et al. 1988

Horm Res

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“…The finding that decreased gonadotrophin responsiveness of the adenylate cyclases was paralleled by a reduction in gonadotrophin receptors made it tempting to postulate that during unilateral cryptorchidism only the gonadotrophin receptors of the receptor-adenylate cyclase complex are lost. The decreased concentration of gonadotrophin receptors and the reduced adenylate cyclase responsiveness to gonadotrophins found in the abdominal testis resemble desensitization of membrane-bound adenylate cyclase systems seen after exposure to high levels of homologous hormone (Hsueh, Dufau & Catt, 1977;Jahnsen et ai, 1980b;Jahnsen, Purvis, Torjesen & Hansson, 1980c). De Kretser et ai (1979) have proposed that the reduction in LH binding seen during cryptorchidism may be due to the elevated concentrations of homologous hormone because LH values are increased considerably during bilateral cryptorchidism (Amatayakul, Ryan, Vozumi & Albert, 1971;Walsh & Swerdloff, 1973;Gupta, Rager, Zarzycki & Eichner, 1975;Gomes & Jain, 1976;de Kretser et ai, 1979;Kerr et ai, 1979).…”

Section: Discussionmentioning

confidence: 96%

Changes in rat testicular adenylate cyclase activities and gonadotrophin binding during unilateral experimental cryptorchidism

Jahnsen¹,

Gordeladze²,

Haug³

et al. 1981

Reproduction

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Unilaterally cryptorchid rats were examined at 3, 8, 15, 22 and 28 days after operation. There was a selective decrease in the adenylate cyclase (ATP pyrophosphate--lyase (cyclizing), EC 4.6.1.1) responses to gonadotrophin stimulation in the abdominal testis. This was associated with a parallel decrease in specific FSH and LH binding. There was no reduction in the response of testicular adenylate cyclases to prostaglandin (PG) E-1 or fluoride stimulation, indicating that both the GTP binding protein (N-component) and the catalytic subunit of the adenylate cyclase complexes were intact. The reduction in FSH-responsive adenylate cyclase activity in the abdominal testis was not due to a change in the Km for adenylate cyclase activation, but was due to a reduction in maximal velocities. Unilateral cryptorchidism was also associated with a rapid decline in soluble Mn2+-dependent adenylate cyclase activity in germ cells (spermatids). By 3 days after operation there was an 82% decrease in germ cell adenylate cyclase activity. The loss of soluble Mn2+-dependent adenylate cyclase activity was associated with a parallel decrease in Sertoli cell secretion of androgen binding protein, indicating that Sertoli cell factors may be important for the maintenance of germ cell adenylate cyclase activity. The desensitization of the gonadotrophin--responsive adenylate cyclases and the loss of gonadotrophin receptors in Leydig and Sertoli cells were not due to changes in plasma gonadotrophin values because LH concentrations were within normal limits and plasma FSH was only marginally elevated in the cryptorchid rats. No significant alterations of any of these parameters were seen in the scrotal testis of unilaterally cryptorchid rats when compared to values for intact controls.

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“…In the testes the contents of gonadotropin binding sites have been shown to change following the administration of gonadotropins [3,4,6,8,12,131. Such studies have been mainly confined to laboratory animals [3,4,8,121, and there have been only a few reports on this change in the human [6, 131. Recently, we reported reduction of testicular follicle-stimulating hormone (FSH) receptors caused by human menopausal gonadotropin (hMG) in infertile men [9].…”

Section: Introductionmentioning

confidence: 99%

Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in Infertile Men

Namiki¹,

Kitamura²,

Miyake³

et al. 1988

Archives of Andrology

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We measured testicular human chorionic gonadotropin (hCG) receptors in 30 infertile men either before or 1, 3, 5, 7, or 14 days after a single administration of 5000 IU of hCG. For 5 days the administration of hCG significantly reduced the testicular binding of I2'I-hCG compared with that of the testes before administration. From the 7th day the binding capacity began to increase and returned to the preadministration level 14 days after the treatment. Occupied hCG binding sites accounted for about half of the reduction in binding sites on the day after administration of hCG. After this time, however, the occupancy did not contribute so much to the reduction in binding sites. These findings suggest that the reduction in testicular hCG binding sites after a single administration of 5000 IU of hCG is due to not only occupancy but also down-regulation of the binding sites.

show abstract

Temporal Relationship Between hCG Induced Desensitization of LH/hCG Responsive Adenylyl Cyclase and Down regulation of LH/hCG Receptors in the Rat Testis

Cited by 21 publications

References 25 publications

Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in vivo and in vitro

Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in vivo and in vitro

Changes in rat testicular adenylate cyclase activities and gonadotrophin binding during unilateral experimental cryptorchidism

Reduction of Testicular Human Chorionic Gonadotropin Receptors by Human Chorionic Gonadotropin in Infertile Men

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