Evaluation of the diuretic effects of crude stem bark extraction of Zanthoxylum heitzii （Rutaceae） in Wistar rats

OBJECTIVE： Zanthoxylum heitzii is a medicinal plant widely used in central Africa for the treatment of many diseases, especially cardiovascular diseases and hypertension. The diuretic effects of crude stern bark extraction were determined and its safety in rats was evaluated. METHODS： The diuretic effects of crude stem bark extraction of Z. heitzii were investigated in Wistar rats （250 g ＋ 10 g） of both sexes. The crude stem bark extraction of Z. heitzii at the doses of 225, 300 and 375 mg/kg was administered to rats at 5 mL/kg body weight. Urine volume was determined 1, 2, 3, 4, 5, 6 and 24 h after administration of the extract. Kinetics of electrolyte elimination in response to a single oral administration dose of acute treatment was measured. The experiments were performed under the same conditions with two synthetic pharmacological diuretics considered as reference （furosemide and hydrochlorothiazide）. Urinary and plasma concentrations of sodium and potassium ions were determined using flame photometry. Concentrations of creatinine, urea, glucose, albumin and electrolytes in the plasma and urine samples were evaluated using a two-way digital bidirectional spectrophotometer. The osmolarity of plasma and urine samples was measured by cytometry using an osmometer. Aldosterone was measured by radioimmunoassay. RESULTS： The plant extract accelerated the elimination of overloaded fluid and increased urine volume and the excretion of Na＋, K＋ and CI 24 h after administration （P〈0.05）. The increase in elimination of Na＋, K＋, and Cl- induced by the extract caused alkalinization of the urine, and showed a strong inhibitory effect on carbonic anhydrase and saluretic. These effects were mainly observed at the dose of 375 mg/kg. At the maximum diuretic response, urinary osmolarity decreased significantly （P 〈 0.05） when compared to controls. The stability of aldosterone level, the absence of correlation with the plasma levels of Na＋, and increased clearance of free water in the animals treated with extract indicated that increased diuresis and natriuresis were tubular in origin. No significant （P 〉 0.05） changes were observed in the body temperature of the animals. CONCLUSION： The significant increase in urine volume 24 h after treatment followed a doseresponse pattern. The excretion of Na＋, K＋ and Cl- caused a decrease in urine osmolarity. The stability of aldosterone, the absence of correlation with the plasma levels of sodium, and increased clearanceof free water