MICROPUNCTURE STUDY OF THE EFFECT OF TRIFLOCIN ON TUBULAR REABSORPTION IN RATS

¹ Department of Pharmacology, University of Tennessee Medical Units, Memphis, Tennessee

The effects of i.v. infusion of 10 mg/kg b.wt. per hr of triflocin on urine flow, glomerular filtration rate, mean arterial blood pressure, and tubular reabsorption and urinary excrecreation of water, urea, sodium and potassium were evaluated in rats using free flow recollection micropuncture techniques. During the administration of this diuretic agent, blood pressure and glomerular filtration rate were depressed while urine flow increased 20-fold. Proximal tubular net transport of sodium, urea and water were not directly affected by the drug. Addition of urea to the loop of Henle fluid from the collecting duct was observed in nondiuretic control conditions, but intrarenal urea recirculation was abolished during diuresis. Triflocin exerted a major inhibitory action on the distal nephron including the distal convoluted tubule and collecting duct. Here, net transtubular movements of all substances studied were markedly depressed. Urinary excretion of sodium, potassium, urea and water were increased under triflocin action. The diuretic effect of triflocin can be attributed to its direct action at two primary sites: first, inhibition of hypertonic sodium reabsorption by the ascending limb of Henle's loop, and second, suppression of reabsorption in the distal nephron. Its other renal actions are most likely indirect, produced through the maintenance of glomerulotubular balance, medullary washout, increased tubular flow rate or altered tubular concentrations of substances.