Renal function studies with propildazine alone and in combination with propranolol in dogs.

The vasodilator antihypertensive propildazine acutely administered in awake dogs (0.1 mg/kg i.v.) produced an arterial blood pressure drop accompanied by tachycardia, decreased urine volume and urinary sodium excretion, and increased urinary potassium excretion. A transient, quickly reversible decrease in glomerular filtration rate was observed; on the contrary, the reduction in urine volume and urinary sodium excretion was longer lasting. There was indirect evidence that sodium retention was mainly caused by increased tubular reabsorption. Decreases in renal resistance, renal extraction of p-aminohippurate, and filtration fraction were observed together with an increase in renal plasma flow. Propildazine at the above dose in combination with propranolol (1 mg/kg i.v.) had a hypotensive effect with a smaller increase in heart rate and without significant variations in urine volume or urinary sodium excretion. These effects could be attributed to antagonism of the reflex-activated sympathoadrenal system by propranolol. In these conditions, the glomerular filtration rate was not significantly modified, while the effects on other renal parameters were similar to those observed with propildazine.