EFFECTS OF BRAIN NATRIURETIC PEPTIDE-45, A CIRCULATING FORM OF RAT BNP, IN SPONTANEOUSLY HYPERTENSIVE RATS

Recently rat brain natriuretic peptide-45(rat BNP-45) was isolated from rat heart, and was 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 a-atrial natriuretic peptide(a-ANP). BNP-45 was a potent natriuretic and hypotensive agent in both strains. The effects were comparable with those of a-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 a-ANP. However, WKY was more susceptible than SHR to BNP-45 for diuresis, natriuresis and urinary cGMP excretion. Moreover, a high dose of BNP-45 led to prolonged lowering of blood pressure and urinary cGMP excretion compared to a-ANP, and those features were prominent in WKY. On the other hand, BNP-45 disappeared more slowly than a-ANP, when the two peptides (2.0μg) were injected intravenously in WKY. Thus, rat BNP-45 and a-ANP had comparable hypotensive and natriuretic potency. However, the action and plasma half-life of rat BNP-45 were more prolonged.