title: Membrane-bound adenylate cyclase activity in the testis of the blue fox.
abstract: Membrane-bound adenylate cyclase (AC) activity was much higher in the presence of Mn2+ than of Mg2+. The Mn2+-sensitive adenylate cyclase (MnAC) showed a linear rate of activity for at least 60 min. In contrast, the Mg2+-sensitive AC (MgAC) displayed a considerable burst in activity, so that after 90 min of activity it was approximately tenfold higher than at the start of incubation. Guanine nucleotides enhanced MgAC activity; 10(-6) to 10(-5) M of 5'-guanylylimidodiphosphate caused a threefold stimulation. The MgAC could be stimulated by hormones (FSH, hCG, PGE1, isoproterenol, glucagon), the highest activation being achieved with FSH. Increasing levels of ATP produced a concentration-dependent increase in MgAC activity. The apparent affinity of the AC for MgATP increased threefold (Km 0.50-0.15 mM) by raising the free Mg2+ concentration from 0.4 to 10.0 mM. The membrane-bound AC of the blue fox testis is thus regulated by hormones, Mg2+, and guanine nucleotides in a similar manner to ACs in other somatic cells and in testes from other species. The high MnAC activity in membrane particles from these testes probably represents membrane-bound AC activity in germ cells. The burst in MgAC activity during incubation may represent proteolytic activation of membrane-bound germ cell AC, with a gradual appearance of Mg2+ sensitivity.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D005589:Foxes / Q000378:metabolism*; D005934:Glucagon / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008345:Manganese / Q000378:metabolism; D008566:Membranes / Q000201:enzymology; D013737:Testis / Q000201:enzymology*; D013997:Time Factors
chemical_list: D006063:Chorionic Gonadotropin; D006165:Guanylyl Imidodiphosphate; D008345:Manganese; D006160:Guanosine Triphosphate; D005640:Follicle Stimulating Hormone; D005934:Glucagon; D000262:Adenylyl Cyclases; D000527:Alprostadil; D008274:Magnesium; D007545:Isoproterenol