Differences between dispersed Leydig cells and intact testes in their sensitivity to gonadotrophin-stimulation in vitro after alteration of LH-receptor numbers.
The sensitivity to hCG-stimulation in vitro of intact hemi-testes and collagenase-dispersed Leydig cells has been compared directly following either an hCG-induced loss of LH-receptors or after a hyperprolactinaemia-induced increase in LH-receptors. Injection of hCG 65 h previously, reduced hCG-binding to dispersed Leydig cells by over 84%. The sensitivity of the steroidogenic response of these cells to hCG-stimulation in vitro was reduced 22-fold whereas intact testes from the same animals showed only a 3-fold reduction in sensitivity to hCG. Dispersed Leydig cells from control rats were 8 times more sensitive to hCG-stimulation than intact testes from the same rats, a difference not evident with hCG-injected rats. In contrast, there was no difference between intact testes and dispersed Leydig cells from control and hCG-injected rats in their sensitivity to stimulation with dibutyryl cyclic AMP in vitro. Induction of hyperprolactinaemia increased hCG-binding to dispersed Leydig cells by 55%. The sensitivity of these cells to hCG-stimulation in vitro was increased by a factor of 4.5, a difference not found with intact testes from the same animals. These results show that experimental manipulation of LH-receptor numbers alters the sensitivity of dispersed Leydig cells, but not of the intact testis, to hCG-stimulation in vitro, a difference which appears to reside at the receptor level. Possible explanations for these findings are discussed together with their implications with respect to the distribution of LH-receptors over the Leydig cell surface.
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D006063:Chorionic Gonadotropin / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis
D006063:Chorionic Gonadotropin; D011956:Receptors, Cell Surface; D013739:Testosterone; D003994:Bucladesine; D007986:Luteinizing Hormone