RENAL HEMODYNAMICS AND SODIUM-EXCRETION AFTER ACUTE AND CHRONIC ADMINISTRATION OF CICLETANINE IN NORMOTENSIVE AND HYPERTENSIVE SUBJECTS

We examined the effects of two therapeutic oral (p.o.) doses of ciclet anine (50 and 100 mg daily) on renal hemodynamics and segmental tubula r handling of sodium. Six normotensive (NT) healthy subjects (group I) received 50 mg cicletanine, and 12 moderately hypertensive (HT) patie nts with normal sodium diet and randomly divided into two groups of 6 were treated either with cicletanine 50 mg (group II) or with cicletan ine 100 mg (group III). Studies were performed both acutely and after 4 weeks of cicletanine administration. After 28-day treatment, blood p ressure (BP) was significantly reduced in HT patients. In NT subjects (group I) and HT patients (groups II and III), acute administration of cicletanine 50 or 100 mg at day 0 did not significantly modify glomer ular filtration rate (GFR) or renal blood flow (RBF), but markedly inc reased fractional excretion of Na (FE(Na)) by 67% in group I and by 62 and 135% in groups II and III, respectively. Fractional distal reabso rption of Na (FDR(Na)) was significantly reduced in the three groups a fter cicletanine administration. After 4-weeks treatment, GFR and RBF were not significantly modified. The increase in Fe-Na and decrease in FDR(Na) were of the same magnitude as that at day 0. No major changes occurred in hormonal profile [renin, aldosterone, atrial natriuretic factor (ANF)]. Even at low doses, cicletanine has a natriuretic effect in NT and HT subjects. Unchanged fractional reabsorption of lithium a nd a significant decrease in FDR(Na) in the three groups suggest that this natriuretic effect occurs at the distal tubule.