Baum M, Quigley R
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063.
J Clin Invest. 1993 Jan;91(1):110-4. doi: 10.1172/JCI116158.
Glucocorticoids have an important role in renal acidification; however, a direct effect of glucocorticoids on proximal convoluted tubule (PCT) acidification has not been directly demonstrated. In the present in vitro microperfusion study PCT from animals receiving dexamethasone (600 micrograms/kg twice daily for 2 d and 2 h before killing) had a significantly higher rate of bicarbonate absorption than did controls (92.0 +/- 13.3 vs 59.9 +/- 3.2 pmol/mm.min, P < 0.01). To examine if glucocorticoids had a direct epithelial action, dexamethasone was added to the bath of PCT perfused in vitro. After 3 h of incubation in paired experiments 10(-6) M and 10(-5) M dexamethasone resulted in an approximately 30% stimulation in the rate of bicarbonate absorption. 10(-7) M dexamethasone and 10(-6) M aldosterone had no effect on bicarbonate absorption. The stimulation of acidification by 10(-5) M dexamethasone was blocked by actinomycin D and cycloheximide. These data are consistent with a direct effect of glucocorticoids on PCT acidification, and this effect is dependent upon protein synthesis.
糖皮质激素在肾脏酸化过程中发挥着重要作用；然而，糖皮质激素对近端肾小管（PCT）酸化的直接作用尚未得到直接证实。在当前的体外微灌注研究中，接受地塞米松（600微克/千克，每日两次，共2天，并在处死前2小时给药）的动物的PCT，其碳酸氢盐吸收率显著高于对照组（92.0±13.3对59.9±3.2皮摩尔/毫米·分钟，P<0.01）。为了检验糖皮质激素是否具有直接的上皮作用，将地塞米松添加到体外灌注的PCT浴液中。在配对实验中孵育3小时后，10^(-6)M和10^(-5)M地塞米松使碳酸氢盐吸收率提高了约30%。10^(-7)M地塞米松和10^(-6)M醛固酮对碳酸氢盐吸收无影响。10^(-5)M地塞米松对酸化的刺激作用被放线菌素D和环己酰亚胺阻断。这些数据与糖皮质激素对PCT酸化的直接作用一致，且这种作用依赖于蛋白质合成。
