Wesson D E
Veterans Administration Medical Center, Baylor College of Medicine, Houston, Texas 77211.
J Clin Invest. 1989 Nov;84(5):1460-9. doi: 10.1172/JCI114321.
Whether augmented bicarbonate reabsorption by renal tubular epithelium contributes to the maintenance of chloride-deplete metabolic alkalosis is not clear. This study used free-flow micropuncture to investigate bicarbonate reabsorption by surface nephron segments in a rat model of diuretic-induced alkalosis compared to control. The proximal and distal nephron of the alkalotic animals had higher values for both delivered load to and absolute reabsorption from these segments. The proximal tubules of alkalotic and control animals had similar values for the slopes of the linear regression of delivered load vs. reabsorption and for the bicarbonate tubular fluid to plasma (TF/P) ratio at the late proximal tubule. By contrast, the corresponding analysis for the distal segment of alkalotic animals revealed a greater slope (0.98 vs. 0.81, P less than 0.003) and a smaller bicarbonate TF/P ratio at the late distal tubule (0.10 vs. 0.16, P less than 0.006). The data indicate that augmented bicarbonate reabsorption by both the proximal and distal nephron contributes to maintaining the alkalosis of this model. The data suggest primary stimulation of bicarbonate reabsorption in the distal nephron and load-dependent reabsorption in the proximal tubule.
肾小管上皮细胞增强的碳酸氢盐重吸收是否有助于维持低氯性代谢性碱中毒尚不清楚。本研究采用自由流微穿刺技术，与对照组相比，在利尿剂诱导的碱中毒大鼠模型中研究表层肾单位节段对碳酸氢盐的重吸收。碱中毒动物的近端和远端肾单位，这些节段的输送负荷和绝对重吸收值均较高。碱中毒动物和对照动物的近端小管，在输送负荷与重吸收的线性回归斜率以及近端小管后期的碳酸氢盐肾小管液与血浆（TF/P）比值方面具有相似的值。相比之下，碱中毒动物远端节段的相应分析显示，远端小管后期的斜率更大（0.98对0.81，P小于0.003），碳酸氢盐TF/P比值更小（0.10对0.16，P小于0.006）。数据表明，近端和远端肾单位增强的碳酸氢盐重吸收有助于维持该模型的碱中毒状态。数据提示远端肾单位碳酸氢盐重吸收的主要刺激以及近端小管中负荷依赖性重吸收。
