The effect of guanine nucleotides on [125I]-angiotensin binding in rat kidney cortex epithelial membranes.

Specific [125I]-angiotensin binding to crude basolateral/brush border membranes of rat kidney cortex was influenced by guanine nucleotides. The order of potency of nucleotides in their ability to decrease specific binding, was Gpp(NH)p greater than GTP greater than or equal to ITP greater than GDP greater than ATP greater than GMP greater than IDP. The kinetic alterations induced by a maximally effective concentration of Gpp(NH)p were: (a) a reduced steady state level of binding and (b) a markedly slower rate of ligand dissociation. The presence of Gpp(NH)p was found to increase the affinity of [125I]-angiotensin binding sites in rat renal cortex membranes. This contrasts with the decreases in affinity of [125I]-angiotensin binding reported in adrenal and mesenteric artery membranes.