Chronic effect of a synthetic atrial natriuretic factor on the development of hypertension in young spontaneously hypertensive rats.

The chronic effect of a synthetic atrial natriuretic factor (ANF) of 25 amino acid residues on the development of hypertension in the 6-week-old spontaneously hypertensive rat (SHR) was assessed. The SHR, on regular diets or given 1% NaCl solution for drinking, were continuously infused with ANF (150 micrograms/kg per day) or vehicle (physiological saline) as controls for up to 14 days. The ANF attenuated transiently the development of hypertension in the sodium-loaded SHR, but the blood pressure returned to control levels by day 5. In SHR on regular diets ANF did not affect the development of hypertension. In addition, ANF did not induce any significant changes in urine volume, fluid intake, urinary sodium and potassium excretion, heart rate, heart weight or haematocrit in young SHR on either normal or increased sodium intake when compared with those in vehicle-infused SHR. These results suggest that ANF may exert some role via a vascular effect at the early stage of development of hypertension in young sodium-loaded SHR.