Chronic effects of synthetic rat atrial natriuretic factor (ANF) on blood pressure and sodium-water excretion in conscious rats

Abstract

We assessed the chronic effects of synthetic rat atrial natriuretic factor consisting of 25-amino acids (ANF) on sodiummwater excretion and blood pressure in conscious rats and also evaluated its antihypertensive effect in rats with hypertension induced by chronic infusion of norepinephrine (NE) Chronic infusion of ANF (150 μg/kg/day) via the jugular vein with an osmotic minipump for up to 3 days failed to affect blood pressure, urine volume, and urinary excretion of sodium, potassium, kallikrein, and prostaglandin E₂ in conscious rats. Although NE (1.8 mg/kg/day i.p.) alone induced a sustained increase in systolic blood pressure (P<0.01), NE (1.8 mg/kg/day i.p.) in combination with ANF (150 μg/kg/day) could not induce an increase in blood pressure. Additional administration of ANF (150 μg/kg/day) to hypertensive rats induced by chronic infusion of NE returned its blood pressure to that of rats administered vehicle alone. These results indicate that chronic infusion of ANF can modulate the vasopressor effect of NE and suggested that endogenous ANF may be involved in the regulation of blood pressure by its vascular action.