OSMOTIC WATER PERMEABILITIES OF BRUSH-BORDER AND BASOLATERAL MEMBRANE-VESICLES FROM RAT RENAL-CORTEX AND SMALL-INTESTINE
OSMOTIC WATER PERMEABILITIES OF BRUSH-BORDER AND BASOLATERAL MEMBRANE-VESICLES FROM RAT RENAL-CORTEX AND SMALL-INTESTINE
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DOI：
10.1007/bf01870707
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发表时间：
1986-01-01
影响因子：
2.4
通讯作者：
VANOS, CH
中科院分区：
文献类型：
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作者：
VANHEESWIJK, MPE;VANOS, CH
用停流分光光度法研究了大鼠小肠和肾皮质刷状缘（BBM）和基底外侧（BLM）膜囊的渗透水通透性。散射光强度被用来跟踪高渗甘露醇溶液渗透扰动后囊泡体积的变化。散射光强度和囊泡体积的关系的理论分析证明了散射光强度的变化的简单指数近似。从指数函数拟合中提取的速率常数与理论预测的最终培养基渗透压摩尔浓度成比例。对于肠膜，光学响应的计算机分析与单指数处理拟合良好。对于肾膜，需要双指数处理，这意味着两种不同的囊泡群。小肠BBM和BLM制备物的Pfvalues相等，为60 μm/sec。对于肾脏制备，快成分、BBM和BLM的Pfvalue为600 μm/sec，慢成分的Pfvalue为50（BBM）和99（BLM）μm/sec。在25至35°C之间，肠膜中水渗透的表观活化能为13.3±0.6，肾膜为1.0±0.3 kCal/mole。巯基汞试剂pCMBS可完全可逆地抑制肾刷状缘标本中的高Pf值。这些观察结果表明，在肠膜中的水通过脂质基质，但在肾质膜水通道可能参与。从肾膜囊泡的高Pf值，可以计算出近端小管的跨细胞水渗透性，其值为10.1 cm/sec。该值允许在体积重吸收期间水流动的完全跨细胞路线。
The osmotic water permeabilityPfof brush border (BBM) and basolateral (BLM) membrane vesicles from rat small intestine and renal cortex was studied by means of stopped-flow spectrophotometry. Scattered light intensity was used to follow vesicular volume changes upon osmotic perturbation with hypertonic mannitol solutions. A theoretical analysis of the relationship of scattered light intensity and vesicular volume justified a simple exponential approximation of the change in scattered light intensity. The rate constants extracted from fits to an exponential function were proportional to the final medium osmolarity as predicted by theory. For intestinal membranes, computer analysis of optical responses fitted well with a single-exponential treatment. For renal membranes a double-exponential treatment was needed, implying two distinct vesicle populations.Pfvalues for BBM and BLM preparations of small intestine were equal and amount to 60 μm/sec. For renal preparations,Pfvalues amount to 600 μm/sec for the fast component, BBM as well as BLM, and to 50 (BBM) and 99 (BLM) μm/sec for the slow component. The apparent activation energy for water permeation in intestinal membranes was 13.3±0.6 and in renal membranes, 1.0±0.3 kCal/mole, between 25 and 35°C. The mercurial sulfhydryl reagentpCMBS inhibited completely and reversibly the highPfvalue in renal brush border preparations. These observations suggest that in intestinal membranes water moves through the lipid matrix but that in renal plasma membranes water channels may be involved. From the highPfvalues of renal membrane vesicles a transcellular water permeability for proximal tubules can be calculated which amounts to ∼1 cm/sec. This value allows for an entirely transcellular route for water flow during volume reabsorption.