Resensitization of the desensitized follicular adenylyl cyclase system to luteinizing hormone.
LH-induced desensitization of the adenylyl cyclase system in a cell-free membrane preparation from preovulatory porcine follicles exhibits a critical dependence upon Mg and ATP (1). The membrane-rich preparation was found to contain endogenous cAMP-dependent and cAMP-independent protein kinases as well as phosphorprotein phosphatases. Endogenous phosphatase activity was enchanced by by Mn2+ and dithiothreitol. The addition of either Mn2+ or dithiothreitol to the porcine follicular membrane preparation incubated under desensitizing conditions promoted a specific concentration-dependent reversal of the LH-induced desensitization of the adenylyl cyclase system. The addition of exogenous phosphoprotein phosphatase, partially purified from procine follicular cytosol, also reversed LH-induced desensitization in a concentration-dependent manner. Boiling of the phophatase preparation prevented reversal of desensitization. The addition of either exogenous beef heart cAMP-dependent protein kinase or heat-stable protein kinase inhibitor did not modify LH-induced desensitization of the follicular adenylyl cyclase system. These results provide indirect evidence that while LH-induced desensitization is not mediated by a cAMP-dependent protein kinase, reversal of desensitization can be promoted by activation of endogenous phosphatase and the addition of a homologous phosphatase preparation.
D000262:Adenylyl Cyclases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D000242:Cyclic AMP / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D005260:Female; D007700:Kinetics; D007986:Luteinizing Hormone / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000201:enzymology*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism; D013552:Swine
D007986:Luteinizing Hormone; D000242:Cyclic AMP; D011494:Protein Kinases; D000262:Adenylyl Cyclases