Distal tubular electrolyte transport during inhibition of renal 11β-hydroxysteroid dehydrogenase

被引:15
作者
Biller, KJ
Unwin, RJ
Shirley, DG
机构
[1] UCL Royal Free & Univ Coll Med Sch, Ctr Nephrol, London W1N 8AA, England
[2] Charing Cross Hosp, Imperial Coll Sch Med, Div Biomed Sci, London W6 8RF, England
关键词
carbenoxolone; sodium reabsorption; potassium secretion; micropuncture; corticosterone;
D O I
10.1152/ajprenal.2001.280.1.F172
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
To test the proposal that the enzyme 11 beta -hydroxysteroid dehydrogenase (11 beta -HSD) confers aldosterone specificity on mineralocorticoid receptors in the distal nephron by inactivating glucocorticoids, we performed a free-flow micropuncture study of distal tubular function in adrenalectomized rats infused with high-dose corticosterone. One-half of the rats were additionally given intravenous carbenoxolone (CBX; 6 mg/h) to inhibit renal 11 beta -HSD activity. Although this maneuver lowered fractional Na(+) excretion (1.1 +/- 0.2 vs. 1.9 +/- 0.2%, P < 0.01), Na(+) reabsorption within the accessible distal tubule was found to be similar in the two groups of animals. In contrast, distal tubular K(+) secretion was enhanced in CBX-treated rats: fractional K(+) deliveries to the early and late distal collection sites in the corticosterone-alone group were 13 +/- 1 and 20 +/- 3%, respectively (not significant), whereas corresponding data in the CBX-treated group were 9 +/- 1 and 24 +/- 2% (P < 0.01). This stimulation of distal K(+) secretion provides the first direct in vivo evidence that 11 beta -HSD normally prevents corticosterone from exerting a mineralocorticoid-like effect in the distal tubule. The reduction in fractional Na(+) excretion during inhibition of 11 beta -HSD, in the absence of a change in end-distal Na(+) delivery, suggests enhanced Na(+) reabsorption in the collecting ducts.
引用
收藏
页码:F172 / F179
页数:8
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