1. The differential effects of extracted and synthetic atrial natriuretic factor (ANF) on arterial blood pressure, natriuresis, and cyclic GMP excretion were studied in normotensive (WKY) and spontaneously hypertensive (SHR and SHRSP) rats.
2. Atrial extracts or synthetic (101–126)-ANF decreased arterial blood pressure in all tested animals, but the blood pressure-lowering effect was more pronounced in hypertensive than in normotensive rats. ANF-induced diuresis and natriuresis were two- to three-fold higher in the hypertensive groups. However, a several-fold increase in total urinary cyclic GMP level after the infusion of ANF was essentially equal in the three groups.
3. Our data suggest that acute infusion of ANF reveals a defect of sodium and water handling in SHR. It is possible that this defect is located at the distal nephron, and is made apparent by the action of ANF on glomeruli via a cyclic GMP-induced vascular effect.