<正>Objective: To compare renal sodium transport

using fractional excretions of lithium（FELi） as a marker of proximal tubule sodium reabsorption

between hypertensive and non-hypertensive ouabain-treated rats and further to elucidate the role of ouabain in pathogenesis of hypertension. Methods: Thirty male Sprague-Dawley rats weighting 180-200 g were randomly divided into normal control group and ouabain treated group. Rats were infused with 1 ml/kg·d normal saline or 27. 8μg/kg·d ouabain in-traperitoneally once a day respectively. Systolic blood pressure （SBP）

heart rate and body weight were recorded weekly. Rats were sacrificed 6 weeks after treatment. Blood and 24-hour urine sample were collected to measure the serum and urinary concentration of sodium

trace lithium and creatinine. Endogenous creatinine clearance rate（Ccr）

fractional excretions of sodium （FENa）

fractional excretions of lithium （FELi） and fractional reabsorption of sodium in the postproximal tubules （FDRNa） were calculated. Ouabain levels of plasma and renal tissue

plasma renin activity

angiotensin I and aldosterone concentration were determined. Results: 65% of the ouabain-treated rats achieved significantly higher SBP after 4 weeks

compared with that of the saline control groups or self baseline （P<0. 01）. But in the other 35% of the ouabain-treated rats

their SBP was similar with control group during the experiment （P>0. 05）. The body weight

heart rate and food intake between the 3 groups were no significant differences （P> 0. 05）. FELi and FDRNa were significantly lower in ouabain-hypertensive group compared with ouabain-non-hypertensive group and control group（P<0. 01 and P<0. 05）. The FEu and FDRn

of ouabain-nonhyper-tensive groups were similar with control group（P>0. 05）. Ccr and FENa were comparable between the 3 groups （P>0. 05）. Plasma and renal tissue ouabain levels

plasma renin activity

angiotensin I and aldosterone contents in ouabain-hypertensive rats were comparable with ouabain-nonhypertensive rats. Conclusion: Increase of proximal tubule sodium reabsorption play an important role in the pathogenesis of ouabain-hypertensive rats. The change of renal sodium transport may result from regulation to renal Na+

K + -ATPase by ouabain.