家兔近端直小管中的钾分泌

Potassium secretion in the rabbit proximal straight tubule.

作者信息

Wasserstein A G, Agus Z S

出版信息

Am J Physiol. 1983 Aug;245(2):F167-74. doi: 10.1152/ajprenal.1983.245.2.F167.

DOI:10.1152/ajprenal.1983.245.2.F167

Abstract

The renal handling of potassium is generally thought to involve proximal reabsorption and distal secretion. To evaluate transport in the pars recta, we perfused S2 and S3 segments from superficial and juxtamedullary proximal straight tubules isolated from the rabbit kidney. The data indicate net potassium secretion in the isolated perfused perfused proximal straight tubule (PST). K+ secretion (JK, pmol X mm-1 X min-1) was -2.51 +/- 0.53 in superficial PST S2 segments, -2.80 +/- 1.05 in superficial PST S3 segments, and -1.36 +/- 0.84 in juxtamedullary PST. Secretion was inhibited by 10(-5) M ouabain in the bath in superficial S2 and S3 segments. When a solution resembling late proximal tubular fluid was perfused in superficial PST, JK fell from -3.86 +/- 1.77 to -0.45 +/- 0.63 pmol X mm-1 X min-1. When luminal flow rate was varied in the physiologic range in individual superficial S2 and S3 segments, JK varied directly; K+ secretion increased by -0.5 pmol X mm-1 X min-1 per 1 nl X min-1 increment in luminal flow, while collected K+ concentration did not vary significantly. When a favorable bath-to-lumen K+ gradient (10 vs. 5 mM) was imposed, K+ secretion was markedly enhanced; when an equal but oppositely directed gradient was imposed, net K+ reabsorption was observed. These data are consistent with a gradient-limited process. In midcortical tubule segments (S2 and S3), 10(-3) M amiloride in perfusate inhibited net K+ secretion from -2.77 +/- 0.52 to -0.18 +/- 1.08 pmol X mm-1 X min-1 and fluid absorption from 0.42 +/- 0.10 to 0.18 +/- 0.05 nl X mm-1 X min-1. Net K+ secretion in S2 and S3 segments of PST may contribute to previously reported K+ secretion prior to the bend of Henle's loop. The magnitude of this process in vivo is uncertain in the absence of measurements of interstitial K+ concentration in the milieu of the PST.

摘要

一般认为，肾脏对钾的处理涉及近端重吸收和远端分泌。为了评估直部的转运情况，我们对从兔肾分离出的浅表和近髓质近端直管的S2和S3段进行了灌注。数据表明，在分离的灌注近端直管（PST）中存在净钾分泌。浅表PST S2段的钾分泌（JK，pmol×mm⁻¹×min⁻¹）为-2.51±0.53，浅表PST S3段为-2.80±1.05，近髓质PST为-1.36±0.84。在浅表S2和S3段的浴液中加入10⁻⁵ M哇巴因可抑制分泌。当在浅表PST中灌注类似近端小管晚期液的溶液时，JK从-3.86±1.77降至-0.45±0.63 pmol×mm⁻¹×min⁻¹。当在单个浅表S2和S3段中，管腔流速在生理范围内变化时，JK呈直接变化；管腔流速每增加1 nl×min⁻¹，钾分泌增加-0.5 pmol×mm⁻¹×min⁻¹，而收集的钾浓度无显著变化。当施加有利的浴液到管腔的钾梯度（10对5 mM）时，钾分泌明显增强；当施加相等但方向相反的梯度时，观察到净钾重吸收。这些数据与梯度限制过程一致。在皮质中部小管段（S2和S3），灌注液中加入10⁻³ M氨氯吡咪可将净钾分泌从-2.77±0.52抑制至-0.18±1.08 pmol×mm⁻¹×min⁻¹，并将液体吸收从0.42±0.10抑制至0.18±0.05 nl×mm⁻¹×min⁻¹。PST的S2和S3段中的净钾分泌可能是先前报道的亨氏袢弯曲之前钾分泌的原因。在没有测量PST环境中间质钾浓度的情况下，该过程在体内的程度尚不确定。