title: Similarities and differences in phorbol ester- and luteinizing-hormone-induced desensitization of rat tumour Leydig-cell adenylate cyclase.
abstract: The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) was shown to mimic luteinizing hormone (LH; lutropin) in causing desensitization of LH-mediated cyclic AMP production in tumour Leydig cells. However, there were differences between LH- and TPA-induced desensitization: (1) TPA induced a more rapid effect than LH; (2) adenosine did not inhibit TPA-induced desensitization, whereas it completely inhibited the LH-induced desensitization; (3) adenylate cyclase activity in plasma membranes from TPA-desensitized cells was not decreased, whereas similar preparations from LH-desensitized cells lost their response to LH and to LH plus guanosine 5'-[beta gamma-imido]triphosphate; TPA-, but not LH-, treated cells had a decreased capacity to respond to cholera toxin and forskolin. These results indicate that LH and phorbol esters induce desensitization of adenylate cyclase in rat tumour Leydig cells by different mechanisms.
authors.forename: C J
authors.initials: CJ
authors.lastname: Dix
authors.forename: A D
authors.initials: AD
authors.lastname: Habberfield
authors.forename: B A
authors.initials: BA
authors.lastname: Cooke
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D066298:In Vitro Techniques; D007984:Leydig Cell Tumor / Q000201:enzymology*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D051381:Rats; D013268:Stimulation, Chemical; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D005576:Colforsin; D007986:Luteinizing Hormone; D002772:Cholera Toxin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D000241:Adenosine; D013755:Tetradecanoylphorbol Acetate