Natriuretic peptides inhibit nicotine-induced whole-cell currents and catecholamine secretion in bovine chromaffin cells: evidence for the involvement of the atrial natriuretic factor R2 receptors.

There is increasing evidence that members of the natriuretic peptide family display sympathoinhibitory activity, but it remains uncertain which receptor pathway is implicated. We performed cyclic GMP production studies with chromaffin cells treated with either atrial natriuretic factor (ANF) or C-type natriuretic peptide (CNP) and found that these cells specifically express the ANFR 1C but not the ANF-R 1A receptor subtype. Evidence for the existence of ANF-R 2 receptors was obtained from patch-clamp experiments where C-ANF, an ANF-R 2 -specific agonist, inhibited nicotinic currents in single isolated chromaffin cells. Involvement of ANF-R 2 receptors in the modulation of nicotinic currents was further supported by the significant loss of this inhibitory activity after the cleavage of the disulfide-bridged structure of C-ANF. This linearized form of C-ANF also displayed a lower binding affinity for ANF-R 2 receptors. Like the patch-clamp studies, secretion experiments demonstrated that both CNP and C-ANF are equally effective in reducing nicotine-evoked catecholamine secretion by cultured chromaffin cells, raising the possibility that this effect of CNP is predominantly mediated by the ANF-R 2 and not the ANF-R 1C receptors. Finally, this response appears to be specific to nicotinic agonists because neither histamine- nor KCl-induced secretions were affected by natriuretic peptides. In the present study, we report (1) the presence of ANF-R 1C and ANF-R 2 receptor subtypes in bovine chromaffin cells, (2) the inhibition by natriuretic peptides of nicotinic whole-cell currents as well as nicotine-induced catecholamine secretion, (3) the possible mediation of these effects by the ANF-R 2 class of receptors, and (4) the specificity of this inhibition to nicotinic agonists. Because bovine chromaffin cells release ANF, BNP, and CNP together with catecholamines, all three peptides might exert negative feedback regulation of catecholamine secretion in an autocrine manner by interacting with the nondiscriminating ANF-R 2 receptor subtype