PARTICIPATION OF PROSTAGLANDINS IN THE EFFECT OF STEVIOSIDE ON RAT RENAL-FUNCTION AND ARTERIAL-PRESSURE

1. The effect of stevioside on renal function was evaluated by clearance techniques in Wistar rats simultaneously with the effect of indomethacin on the renal action of stevioside. The indomethacin experiments consisted of four consecutive periods: (C) control; (S), in which stevioside (16 mg/kg) was continuously infused; (S + I1) and (S + I2) in which indomethacin was infused systemically without interrupting stevioside infusion. Mean arterial pressure (MAP) and renal function parameters were measured. 2. Administration of stevioside resulted in a statistically significant dose-related decrease in MAP (121 +/- 2.30, N = 7 for 4 mg/kg stevioside to 72 +/- 4.79 mmHg, N = 7 for 16 mg/kg stevioside) and an increase in renal plasma flow (RPF) (10.27 +/- 1.21, N = 7 for 4 mg/kg stevioside to 26.28 +/- 2.87 ml min-1 kg-1, N = 7 for 16 mg/kg stevioside), with no change in glomerular filtration rate (GFR). Stevioside also increased fractional sodium (Fe(Na+)) and potassium (Fe(K+)) excretion as well as urine flow (V/GFR). 3. The decrease in MAP (control, 121 +/- 0.93, N = 7; stevioside, 91 +/- 2.48 mmHg) and increase in RPF (control, 14.21 +/- 1.41, N = 7; stevioside, 32.53 +/- 2.84 mmHg) induced by stevioside (16 mg/kg) were inhibited by simultaneous administration of indomethacin (2 mg/kg), but GFR was not affected. The diuretic, natriuretic and kaliuretic effects of stevioside were also abolished by indomethacin. 4. We conclude that stevioside behaves like a typical vasodilator substance, causing changes in MAP, diuresis, natriuresis and kaliuresis per ml of GFR, and these effects probably depend on prostaglandins.