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Investigates guanylate cyclase activity in human erythrocytes by evaluating the intracellular guanosine 3',5'-cyclic monophosphate (cGMP) content in the presence of agents that exert specific effects on soluble or particulate guanylate cyclase. Increase in intraerythrocyte cGMP content; Atrial natriuretic peptide; Activation of the erythrocyte Na+/H+ exchange.

Human atrial natriuretic peptide (ANP) fragments ANP-(127-150) or ANP-III and ANP-(127-149) or ANP-II activate Na+/H+ exchange in human erythrocytes at concentrations as low as 1 pM. Both ANP-(127-147) or ANP-I and ANP-(129-150) or des-Ser5, Ser6-ANP-III have no effect on erythrocyte Na+/H+ exchange. ANP-III also produces a time-dependent increase of intraerythrocyte guanosine 3′,5′-phosphate (cGMP) concentration. M&B 22,948, a specific inhibitor of cGMP phosphodiesterase, increases Na+/H+ exchange and the intracellular concentration of cGMP. Both 8-bromoguanosine 3',5'-phosphate (8-Br-cGMP) and dibutyryl-cGMP mimic the effect of ANP-III on erythrocyte Na+/H+ exchange. Our data suggest that human erythrocytes possess guanylate-cyclase activity stimulated by ANP-III and that activation of Na+/H+ exchange by this peptide is mediated by cGMP. Human erythrocytes display a high degree of sensitivity to ANP-III or ANP-II and a specificity for ANP-fragment structures just as cells with established ANP-specific receptors. [ABSTRACT FROM AUTHOR]