Inhibition of I-Labeled human choronic gonadotropin binding to gonadal receptors by a factor obtained from rat testicular tissue

Abstract

Inhibition of I-Labeled human choronic gonadotropin binding to gonadal receptors by a factor obtained from rat testicular tissue Rojas, Francisco J.; Moretti Rojas, Inés; Arata de Bellabarba, Gabriela y Bishop, Walter

Abstract

The ability of a factor obtained from a 105,000 xg supernatant of rat testis, to inhibit the hCG nature, and presented a molecular weight under 12,000. Binding studies indicated that the hCG binding inhibitor interfered with the formation of the hormone - receptor complex mainly by competing with hCG for the same binding sites. Consequently, it was demonstrated that the inhibitor prevented the interaction of hCG and its receptor in both testicular and ovarian tissues. Under in vitro binding conditions, it was observed that as the quantities of the inhibitor increased during the first incubation with testicular homogenate, and after removing the inhibitor and washing the pellet, less and less of the added labeled hCG was bound during the second incubation step. On the other hand, the hormone already bound to the tissue during the first incubation could not be displaced by increasing amounts of the inhibitors in the second incubation. Thus, binding of the inhibitor, or hormone, to the tissue in the first step was not readily exchangeable with the subsequent binding to LH / hCG receptors may proceed in a irreversible manner...