Inactivation of porcine corpus luteum lutropin receptors by a microsomal enzyme. Activation in ageing and regressing corpora lutea.
The binding of 125I-labelled human choriogonadotropin (hCG) to homogenates of porcine corpora lutea showed a marked departure from ideal behaviour, due to a time- and temperature-dependent inactivation of both free hormone and unoccupied receptors. Occupied receptors were not affected. Lutropin (LH)-receptor-inactivating activity was detected after preincubation of homogenates, particulate fractions and microsomes, but little activity could be demonstrated in cytosol fractions. Inactivation was dependent on the temperature and pH of preincubation, and on tissue concentration: LH-receptor inactivation was first-order with respect to preincubation time. Lutropin-receptor-inactivating activity was low in early-luteal and mid-luteal phase in pig corpora lutea, but was increased significantly in late-luteal and regressing corpora lutea.
D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism; D003338:Corpus Luteum / Q000502:physiology*; D003600:Cytosol / Q000201:enzymology; D004971:Estrus; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011974:Receptors, LH; D013552:Swine
D006063:Chorionic Gonadotropin; D011956:Receptors, Cell Surface; D011974:Receptors, LH