Renal and blood pressure responses to synthetic atrial natriuretic factor in spontaneously hypertensive rats.

Atrial natriuretic factor (ANF) is a potent natriuretic and vasorelaxant agent that also stimulates guanosine 3',5'-cyclic monophosphate (cGMP) excretion in normotensive animals. These properties suggest that ANF may be involved in the regulation of blood pressure. To test a pure preparation of ANF in both normotensive and hypertensive animals, a synthetic 26 amino acid peptide (sANF) contained within endogenous rat ANF was infused intravenously into conscious Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) at doses from 12 to 190 pmol/minute. Mean arterial pressure fell progressively as doses of sANF were increased until maximum responses of -41 +/- 5 mm Hg and -29 +/- 5 mm Hg were obtained during infusion of 95 pmol/minute sANF in SHR and WKY, respectively. Heart rate was not significantly affected in either group. At sANF doses of 12 to 50 pmol/minute, urinary electrolyte excretion rose in a dose-related fashion and was similar in WKY and SHR. At infusions of 95 to 190 pmol/minute, the diuretic and saluretic responses were diminished in the hypertensive animals. Only the 190 pmol/minute sANF dose significantly enhanced cGMP excretion in SHR (p less than 0.05); however, in WKY urinary cGMP excretion was elevated in a dose-related fashion. At the highest sANF dose, cGMP excretion was approximately 15 times that observed in the pretreatment urine. The differences in the renal and blood pressure responses to sANF in SHR and WKY suggest that the actions of endogenous ANF may be altered in hypertension.