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

Atrial natriuretic peptide (ANP, 10 and 50 ng/kg per min), infused into the renal artery, suppressed decreases in renal blood flow induced by intrarenal arterial injection of angiotensin II (Ang II, 25-100 ng) and norepinephrine (NE, 0.25-1 microgram) in anesthetized dogs. Sodium nitroprusside (SNP, 0.1-5.0 micrograms/kg per min) slightly attenuated the blood flow response to Ang II but not the response to NE. 8-Bromo cyclic GMP (8bcGMP, 0.5-25 micrograms/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 micrograms), nifedipine pretreatment (20 micrograms/kg plus 1 microgram/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 Ca2+ channels.