A crude extract of Stevia rebaudiana increases the renal plasma flow of normal and hypertensive rats

ABSTRACT

The effect of S. rebaudiana extract on renal function was evaluated in normotensive and in experimental renal hypertensive rats (GII) using clearance techniques. Experiments were performed on male Wistar rats weighing 300-330 g (10 animals per group). Goldblatt GH experimental hypertension was induced by placing a silver clip with an internal gap of 0.25 mm around the left renal artery under ether anesthesia. The contralateral kidney was left untouched. Stevia was administered 1012 weeks after clipping. Oral administration of Stevia extract, corresponding to 2.67 g dry leaves/day for 30 days, resulted in a significant decrease in mean arterial pressure in both the normo- (N) and hypertensive rats (H) (N rats 113 ñ 3.0 mmHg in the control (C) group vs 69.5 ñ 4.0 mmHg in the Stevia (S) group; H rats 155 ñ 3.0 mmHg in C vs 108 ñ 4.0 mmHg in S; P<0.05). Glomerular flltration rate was constant in the N rats and increased significantly in the H rats afterStevia treatment (6.47 ñ 1.29 vs 14.2 ñ 1.33 ml min-1 kg-1 in the C and S groups, respectively, P<0.05). Normo- and hypertensive rats presented an increase in renal plasma flow following oral Stevia administration (N rats 16.4 ñ 3.10 ml min-1 kg-1 in the C group vs 33.3 ñ 3.20 ml min-1 kg-1 in the S group,P<0.05; H rats 19.30ñ2.45 ml min-lkg-1 in the C group vs 37.0 ñ 3.93 ml min-1 kg-1 in the S group, P<0.05). Stevia administration provoked an increase in urinary flow in both N and H animais (1.37 ñ O.08 per cent vs 2.32 ñ 0.11 per cent P<0.05 and 1.47 ñ 0.07 per cent vs 2.96 ñ O.13 per cent, P<0.05 in N and H rats, respectively). Sodium excretion increased in N and H animals after Stevia treatment (N rats O.61 ñ O.07 per cent in the C group vs 1.55 ñ 0.20 per cent in the S group, P<0.05; H rats 0.70 ñ 0.1O per cent in the C group vs 2.22 ñ O.45 per cent in the S group, P<0.05). These results are consistent with impairtnent of a renal autoregulation mechanism in this hypertensive model after Stevia administration. In conclusion, it was shown that Stevia extract, at doses higher than used for sweetening purposes, is a vasodilator agent in - and hypertensive animals.