Melis M S, Rocha S T, Augusto A
Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil, 14030-000.
Braz J Biol. 2009 May;69(2):371-4. doi: 10.1590/s1519-69842009000200019.
Stevia rebaudiana, a South American plant normally used as a natural herbal sweetener, has been suggested as exerting beneficial effects on human health, including as an antihypertensive and antihyperglycemic. The present experiment was undertaken to evaluate the renal excretion of steviol, the aglycone of several natural products extracted from the leaves of S. rebaudiana, and to clarify the actual participation of this compound on the renal excretion of glucose in rats, which has been previously suggested as the preferential action of steviol on the Na+-glucose renal tubular transport system. Steviol was obtained by enzymatic hydrolysis of stevioside with pectinase. Thirty normal male Wistar rats weighing 345 g were used. After a control period, steviol was infused iv at three doses (0.5, 1.0 and 3.0 mg.kg-1/h), according to classical clearance techniques. During all the experiments no significant changes in inulin clearance (Cin) and p-aminohipuric acid clearance (C PAH) were observed. Administration of steviol resulted in a statistically significant increase in the fractional sodium excretion (FeNa+), fractional potassium excretion (FeK+), urinary flow as percent of glomerular filtration rate (V/GFR) and glucose clearance (C G) when compared to controls, but these effects were absent with the dose of 0.5 mg.kg-1/h. The steviol clearance (C S) was higher than the Cin and lower than the C PAH at all the doses employed in this study. The data suggest that steviol is secreted by renal tubular epithelium, causing diuresis, natriuresis, kaliuresis and a fall in renal tubular reabsorption of glucose.
甜叶菊是一种南美洲植物，通常用作天然草本甜味剂，有人认为它对人体健康有益，包括具有抗高血压和降血糖作用。本实验旨在评估甜菊醇（从甜叶菊叶子中提取的几种天然产物的苷元）的肾脏排泄情况，并阐明该化合物在大鼠肾脏葡萄糖排泄中的实际作用，此前有人认为甜菊醇对钠 - 葡萄糖肾小管转运系统具有优先作用。甜菊醇通过用果胶酶对甜菊糖苷进行酶促水解获得。使用了30只体重345克的正常雄性Wistar大鼠。在对照期后，按照经典清除技术以三种剂量（0.5、1.0和3.0毫克·千克⁻¹·小时⁻¹）静脉输注甜菊醇。在所有实验过程中，未观察到菊粉清除率（Cin）和对氨基马尿酸清除率（C PAH）有显著变化。与对照组相比，甜菊醇给药导致钠排泄分数（FeNa⁺）、钾排泄分数（FeK⁺）、尿流量占肾小球滤过率的百分比（V/GFR）和葡萄糖清除率（C G）在统计学上显著增加，但0.5毫克·千克⁻¹·小时⁻¹剂量时没有这些作用。在本研究使用的所有剂量下，甜菊醇清除率（C S）高于Cin且低于C PAH。数据表明甜菊醇由肾小管上皮分泌，导致利尿、利钠、利钾以及肾小管对葡萄糖重吸收减少。
