The vasodepressor action of prostacyclin (PGI2) and its effect on plasma angiotensin II and vasopressin in unanaesthetized normotensive and hypertensive rats.

The action of prostacyclin (PGI2) on arterial pressure, heart rate, plasma concentration of angiotensin II and vasopressin was studied in groups of normal, renal hypertensive and DOC hypertensive rats. PGI2 was given by continuous iv. infusion at successive doses of 0.25, 0.5 and 1.0 microgram/kg x min, each rate for one hour. Arterial pressure was reduced to normal or below normal in the hypertensive rats, though the fall of blood pressure was greatest in the DOC hypertensive animals. Mean arterial pressure at the end of infusion was 89 mm Hg for normal rats, 87 mm Hg for renal hypertensive rats and 69 mm Hg for DOC hypertensive rats. Diastolic pressure fell more than systolic pressure suggesting a vasodilator mechanism. Heart rate was reduced significantly at the end of the infusion in the three groups of rats. Prostacyclin was also infused for 3 hours at a constant rate of 0.5 microgram/kg x min. The arterial pressure lowering effect was maintained throughout the infusion period.