title: Lutropin receptors from male and female tissues: different responses to a lutropin receptor binding inhibitor.
abstract: An inhibitor for lutropin receptor site binding (LH-RBI), which strongly inhibited the binding of 125I-labeled ovine lutropin ([125I]oLH) to ovarian LH receptors, did not inhibit the [125I]oLH binding to testicular LH receptors. Preincubation of the LH-RBI with [125I]oLH did not affect the binding of preincubated ]125I]oLH to ovarian LH receptors. No inhibition of [125I]oLH binding to testicular LH receptors was observed even uhen the concentration of LH-RBI was significantly increased or when the testicular LH receptors uere first incubated with LH-RBI prior to the addition of [125I]oLH and a second incubation. Scatchard analysis revealed that the dissociation constant of [125I]oLH binding was essentially the same in the presence or absence of LH-RBI. The results suggest that: (i) the lutropin receptor of ovaries, but not of testes, has a specific LH-RBI binding site in addition to the lutropin binding site, and (ii) the binding of the LH-RBI produces an "allosteric" type of inhibition to the binding of lutropin at the lutropin binding site.
mesh_terms: D000818:Animals; D005260:Female; D007986:Luteinizing Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D010053:Ovary / Q000378:metabolism*; D011247:Pregnancy; D011555:Pseudopregnancy; D051381:Rats; D011956:Receptors, Cell Surface; D013737:Testis / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D007986:Luteinizing Hormone