Effects of indomethacin, renal denervation, and propranolol on plasma renin activity in conscious dogs with chronic thoracic caval constriction.

Abstract

The role of renal prostaglandins and the adrenergic nervous system in the control of renin release was studied in conscious dogs with thoracic caval constriction. Indomethacin reduced plasma renin activity (PRA) in intact animals with thoracic caval constriction by 43% but failed to change PRA after surgical renal denervation and during chronic propranolol administration; adrenergic blockade reduced the initial control level of PRA before indomethacin from 15 to 4 ng angiotensin I/ml per hr. Renal hemodynamic function was markedly reduced by indomethacin both before and after adrenergic blockade. These observations indicate that prostaglandins are involved in the control of renin release, but they appear to have a more important role in the control of renal arterial resistance. The adrenergic nervous system also plays a role in the hyperreninemia of caval constriction and, possibly, a greater role than the renal prostaglandins. In the first experimental design, surgical renal denervation and daily oral propranolol administration in dogs with caval constriction reduced PRA to normal in two of seven dogs and a natriuresis occurred. In four of the five remaining animals, PRA fell, but not to normal, and renal sodium excretion failed to increase. In a second experimental design, the kidneys were denervated and propranolol was given before the dogs were subjected to caval constriction and propranolol was continued for 5 days; PRA increased markedly, sodium retention occurred, and ascites formed. Under these circumstances, compensatory mechanisms secondary to caval constriction led to increased PRA in spite of adrenergic blockade.