Effects of brain natriuretic peptide-45, a circulating form of rat brain natriuretic peptide, in spontaneously hypertensive rats

Rat brain natriuretic peptide-45 (rat BNP-45) has recently been isolated from rat heart and shown to be a circulating form of rat BNP. We investigated the effects of rat BNP-45 in anesthetized spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) and compared them with those of rat alpha-atrial natriuretic peptide (alpha-ANP). BNP-45 was a potent natriuretic and hypotensive agent in both strains. The effects were comparable with those of alpha-ANP and were far greater than those of porcine BNP-26 reported previously. In SHR blood pressure decreased more than in WKY following injection of the highest dose (2.0 nmol/kg) of BNP-45 or alpha-ANP. However, WKY were more susceptible than SHR to BNP-45 for diuresis, natriuresis and urinary cGMP excretion. Moreover, a high dose of BNP-45 led to a prolonged lowering of blood pressure and urinary cGMP excretion compared to alpha-ANP, and these features were prominent in WKY. BNP-45 disappeared more slowly than alpha-ANP when the two peptide (2.0 micrograms) were injected i.v. in WKY. Thus, rat BNP-45 and alpha-ANP had comparable hypotensive and natriuretic potency; however, the action and plasma half-life of rat BNP-45 were more prolonged.