Hypotensive and uric acid-retaining effects of trichlormethiazide under dietary sodium restriction in spontaneously hypertensive rats.

In order to evaluate both the hypotensive and uric acid-retaining effects of thiazide diuretics in an animal model with hypertension, the effects of trichlormethiazide were studied using spontaneously hypertensive rats (SHR) under dietary sodium restriction. Trichlormethiazide was dosed daily for two weeks at 0.05, 0.5, 3 and 10 mg/kg, p.o. All doses caused obvious natriuresis, while an increase of urine volume was observed only at 3 and 10 mg/kg. The hypotensive effect, which was estimated at day 6 and 13, was recognized at doses of more than 0.5 mg/kg. At the end of the dosing, the hematocrit value of all medicated groups rose, and both the uric acid excretory capacity, estimated by the clearance values of inulin and uric acid, and the plasma potassium level clearly decreased at 3 and 10 mg/kg. A detailed study using a dose of 3 mg/kg showed shifts of the cumulative sodium and potassium balances to negative directions against the control group. Thus, trichlormethiazide-treated SHR under dietary sodium restriction showed both a hypotensive effect which might be due to the natriuresis and a tendency toward undesirable side effects such as hypokalemia and hyperuricemia. As there is no practical method in animal studies for simultaneously proving hypotensive and uric acid-retaining effects of diuretic antihypertensives, the findings of the present study might aid in the evaluation of diuretics more useful than the thiazides.