Characterization of Relaxant Responses to Natriuretic Peptides in the Human Microcirculation In Vitro and In Vivo

OBJECTIVE: We characterized the vasodilatory effects of ANP, BNP, and CNP in human subcutaneous arterioles in vitro and the cutaneous microcirculation in vivo.

METHODS: The in vitro experiments were performed using wire myography and the responses were characterized by the use of inhibitors for nitric oxide (L-NAME), prostaglandin synthesis (indomethacin), or the endothelium-derived hyperpolarization factor. In vivo, the vasorelaxant effect of iontophoretically administrated BNP or CNP was measured with a noninvasive laser Doppler technique. Involvement of nitric oxide or prostaglandins was assessed by L-NAME or indomethacin given by iontophoresis.

RESULTS: In vitro all three peptides showed significant vasodilatation with the efficacy order: CNP > BNP = ANP. The BNP-induced vasodilatation, but not that of ANP or CNP, was significantly reduced by pretreatment with indomethacin or L-NAME. In vivo administration of BNP induced a marked vasodilatory response that was attenuated by local pretreatment of L-NAME. Indomethacin by itself resulted in increased cutaneous perfusion.

CONCLUSIONS: NPs are potent vasodilators in the human subcutaneous circulation. The response to BNP differs from that of the other peptides as it seems dependent on cyclooxygenase products and nitric oxide.