离体灌注青蛙近端肾小管对PAH的转运及液体吸收

PAH transport and fluid absorption by isolated perfused frog proximal renal tubules.

作者信息

Irish J M, Dantzler W H

出版信息

Am J Physiol. 1976 Jun;230(6):1509-16. doi: 10.1152/ajplegacy.1976.230.6.1509.

DOI:10.1152/ajplegacy.1976.230.6.1509

Abstract

Para-aminohippurate (PAH) transport and fluid absorption were studied in isolated perfused frog (Rana catesbeiana) proximal renal tubules. With 2 X 10(-5) M PAH in the bath, tubule fluid-to-bath (TF/B) concentration ratios averaged 3.0 and net secretion averaged 746 X 10(-15) mol min(-1) mm(-1) in the proximal tubule. Net PAH secretion did not vary with perfusion rate. During PAH secretion, cell water PAH concentration exceeded that in the tubular fluid or bath, suggesting active transport into cells and subsequent diffusion into lumen. In accordance with this concept, luminal membrane permeability (3.8 X 10(-5) cm s(-1) calculated from perfusion studies was about 6 times greater than peritubular membrane permeability (0.66 X 10(-5) cm s(-1)) determined from studies of PAH efflux from tubules with oil-filled lumens. Net transepithelial PAH transport saturated at bath concentration of about 6 X 10(-5) M. Addition of 20 mM urea to PAH bath concentration of 2 X 10(-5) M reduced net PAH secretion by 32%. Fluid absorption in proximal tubules averaged 0.34 nl min(-1) mm(-1). Ouabain (10(-4), 10(-5), or 10(-6) M) added to bath blocked fluid absorption. Fluid absorption was partially restored following removal of ouabain.

摘要

在离体灌注的牛蛙近端肾小管中研究了对氨基马尿酸（PAH）转运和液体吸收情况。浴液中PAH浓度为2×10⁻⁵M时，近端小管的小管液与浴液（TF/B）浓度比平均为3.0，净分泌平均为746×10⁻¹⁵mol·min⁻¹·mm⁻¹。PAH净分泌不随灌注速率变化。在PAH分泌过程中，细胞内水相PAH浓度超过小管液或浴液中的浓度，提示PAH主动转运进入细胞，随后扩散至管腔。根据这一概念，从灌注研究计算得到的管腔膜通透性（3.8×10⁻⁵cm·s⁻¹）约为从充满油的管腔的小管中PAH流出研究确定的周缘膜通透性（0.66×10⁻⁵cm·s⁻¹）的6倍。跨上皮PAH净转运在浴液浓度约为6×10⁻⁵M时达到饱和。向PAH浴液浓度为2×10⁻⁵M中添加20 mM尿素可使PAH净分泌减少32%。近端小管中的液体吸收平均为0.34 nl·min⁻¹·mm⁻¹。向浴液中添加哇巴因（10⁻⁴、10⁻⁵或10⁻⁶M）可阻断液体吸收。去除哇巴因后液体吸收部分恢复。