Abstract
In intact male rats (IMR) a single injection of hCG (10-500 IU) induced a peak of plasma testosterone (T) 2 hrs later. Plasma T decrease thereafter in spite of high levels of hCG, indicating steroidogenic refractoriness to hCG stimulation. Leydig cells isolated from testis of hCG treated rats were insensitive to in vitro stimulation by hCG, cholera toxin and dibutyryl cAMP. In addition a decrease in the number of hCG binding sites appears some hours later than refractoriness. Responsiveness to hCG was restaured 4 to 5 days after hCG injection. In hypophysectomized (Hpx) rats the early T response was 20 times lower than in IMR. However hCG induced the same refractoriness than in IMR, while at the end of this period T response to hCG was similar to that of IMR. It is concluded that hCG induced refractoriness is related to three phenomena : modification of the coupling between the hCG binding site and adenylate cyclase, abnormality of some step beyond cAMP formation and decrease of the hCG binding sites. In addition, in Hpx rats a “maturation” of the steroidogenic pathways occurs during the refractoriness period.
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Saez, J., Haour, F., Cathiard, A. et al. hCG-induced steroidogenic refractoriness of Leydig cells: I. Experimental evidence of receptor and post-receptor modulation of gonadotropin action. Pediatr Res 12, 1086 (1978). https://doi.org/10.1203/00006450-197811000-00027
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DOI: https://doi.org/10.1203/00006450-197811000-00027