Atrial natriuretic peptide suppresses renal vasoconstriction induced by angiotensin II and norepinephrine in dogs

Atrial natriuretic peptidc (ANP, 10 and 50 ng/kg per min), infused into the renal artery, suppressed decreases in renal blood flow induced by intrarcnal arterial injection of angiotensin II (Ang II, 25–100 ng) and norepinephrine (NE, 0.25–1 μg) in anesthetized dogs. Sodium nitroprusside (SNP, 0.1–5.0 μg/kg per min) slightly attenuated the blood flow response to Ang II but not the response to NE. 8-Bromo cyclic GMP (SbcGMP, 0.5–25 μg/kg per min) did not suppress the blood flow response to Ang II. Although at a high dose ANP attenuated the blood flow response to Bay K 8644 (1–4 μg), nifedipine pretreatment (20 μg/kg plus 1 μg/kg per min i.v.) did not affect the inhibitory effect of ANP on the NE-induced response. The vaso-inhibitory effects of ANP therefore could not be related exclusively to stimulation of cGMP production or inhibition of voltage-dependent Ca 2+ channels.