AREGU May 45/5

Woods, Robyn L., and Marcus J. M. Jones. Atrial, B-type, and C-type natriuretic peptides cause mesenteric vasoconstriction in conscious dogs. Am. J. Physiol. 276 (Regulatory Integrative Comp. Physiol. 45): R1443–R1452, 1999.— Cardiovascular responses were compared with equimolar infusions of B-type (BNP) and C-type (CNP) with atrial natriuretic peptide (ANP) in conscious, instrumented dogs. On separate days, each natriuretic peptide or vehicle was infused (intravenously) at step-up doses of 2, 5, 10, and 20 pmol ·kg21 ·min21 (20 min each dose) to increase circulating levels of the infused peptide from ,2to 20-fold. Like ANP, infusions of BNP caused dose-related increases (P , 0.05) in mesenteric vascular resistance, urine flow, natriuresis, and hematocrit (changes at highest doses were 60 6 9, 334 6 113, 313 6 173, and 12 6 2%, respectively). BNP also lowered (P , 0.05) plasma renin activity (243 6 11%) and arterial pressure (210 6 3%). Effects of BNP were independent of reflex sympathetic activation, since autonomic ganglion blockade did not attenuate the responses. CNP infusions had little effect except to increase (P , 0.05) mesenteric vascular resistance (27 6 10%) and plasma ANP (41 6 7%). Cardiovascular actions of BNP, like those of ANP, counteract the renin-ANG system and may protect the heart by lowering cardiac preload (venous return) and afterload (arterial pressure) while maintaining blood flow to extrasplanchnic regions.