Pharmacological profile of HS-142-1, a novel nonpeptide atrial natriuretic peptide antagonist of microbial origin. I. Selective inhibition of the actions of natriuretic peptides in anesthetized rats.

HS-142-1, a novel polysaccharide, isolated from the culture broth of Aureobasidium pullulans var. melanigenum, has been found to inhibit selectively the binding of [125I]atrial natriuretic peptide (ANP) to the guanylyl cyclase-linked ANP receptor (ANP-B receptor) and production of cyclic GMP by ANP. The effect of this compound on renal and vascular actions evoked by exogenously administered natriuretic peptides was examined in anesthetized rats. The increase in urine flow and in the urinary excretion of sodium elicited by human ANP or porcine brain natriuretic peptide was prevented by pretreatment with HS-142-1. The prevention was accompanied by the inhibition of increase in urinary cyclic GMP excretion. In addition, these renal responses were rapidly reversed by an injection of HS-142-1 during ANP infusion. Higher doses of HS-142-1 did not alter the increase in urine flow and in the urinary excretion of sodium evoked by furosemide, and HS-142-1 alone showed no significant change in these renal parameters. Hypotensive action elicited by human ANP was also prevented by the pretreatment with HS-142-1 and rapidly reversed by treatment with HS-142-1 during ANP infusion. These results clearly demonstrate that HS-142-1 acts as an antagonist for ANP-B receptor in vivo. HS-142-1, then, provides a new tool for the study of the physiological and pathophysiological roles of ANP.