Calcium-mediated Interactions between the Antidiuretic Hormone and Renal Plasma Membranes

摘要: Abstract The antidiuretic hormone-stimulated adenylate cyclase system has been characterized in a purified preparation of porcine renal plasma membranes. Adenylate activity was linear over membrane protein concentration from 30 to 300 µg, and maximal enzyme occurred at approximately 7 x 10-4 m ATP. Activation the by sodium fluoride about 10-fold produced 10 12 mm fluoride. stimulated 3-fold hormone. One-half stimulation hormone measured 2.2 10-8 Calcium exhibited an inhibitory effect upon concentrations metal ion above 10-6 m, but it little or no inhibition fluoride-stimulated system. chelating agent, ethylene glycol-bis(β-aminoethyl ether)-N,N'tetraacetic acid, 1 mm, completely inhibited adenyl cyclase. chelator-inhibited restored increasing calcium. Binding tritiated membranes centrifugation techniques filtration through Millipore filters. Both methods demonstrated that binding level 0.5 pmole per mg when added half-maximal rates association dissociation for interaction between were measured. equilibrium reached after min 37°. Dissociation bound shown be 100% complete min. Graphical analysis time course kinetics reaction follows simple first order rate equation. Neither adrenocorticotropic nor calcitonin exchanged with its site, indicating receptor sites exhibit specificity millimolar range ADH However, ether)-N,N'-tetraacetic acid same which had These results suggest calcium plays multiple regulatory roles inhibiting lower mediating locus within matrix site occupied