Efeito das saponinas triterpênicas isoladas das raizes da ampelozizyphus amazonicus ducke sobre a função renal

Abstract

Objective: In this study, we have investigated the effect of crude extract of roots of Ampelozizyphus amazonicus Ducke (CEAaD) and of saponins isolated from CEAaD (SAPAaD), on renal function in rats as well as possible mechanisms SAPAaD effects occur. Materials and Methods: Wistar rats (250-350g) were volume expanded with 0.9% NaCl (4% of body weight) in the absence and presence of CEAaD or SAPAaD given bygavage. Rats were individually housed in metabolic cages and urine flow (UF) was measured every 30 min throughout the experiment (3 h). SAPAaD (50 mg/kg) effect, 90 or 60 min after gavage, also was investigated on the following parameters: GFR (creatinin clearance), Na+ e K+ (flame photometer), osmolality (freezer point osmometry), plasma and atrial content of ANP and urinary urodilatin (RIA). In addition, after SAPAaD treatment, kidneys were removed for further morphologicalanalysis and determination of ATPases (Na+ ATPase e (Na++K+)-ATPase) activities. Results: Contrarily to CEAaD, which increased diuresis, SAPAaD reduced UF in a dose-dependent manner. SAPAaD (50 mg/kg) reduced UF from 371.3 (CTL) to 155.6 ml.min (area under curve) (p< 0.05). SAPAaD also became CH2O more negative (-5.56± 0.45 vs -3.21 ± 0.73 ml/min, CTL) (p = 0.025), increased fractional excretion of Na+ (2.17± 0.43 vs 1.01 ± 0.27%, CTL) (p=0.048) and of K+ (131.5 ± 17.5 vs 60.1 ± 20.0%, CTL) (p=0.028), increased Na+ ATPase activity (25.0 ± 5.9, CTL, vs 52.7 ± 8.9 nmolPi x mg-1x min-1, p=0.049) and decreased urinary urodilatin (792 ± 132, CTL, vs 299 ± 88 g/ml, p=0.01).Conclusion: SAPAaD may reduce UF by increasing water reabsorption in renal tubules. Antidiuretic effect of SAPAaD may be due to an increase in renal activities of ATPases and/or a decrease in renal urodilatin.