VOLUME-ACTIVATED, GADOLINIUM-SENSITIVE WHOLE-CELL CURRENTS IN SINGLE PROXIMAL CELLS OF FROG KIDNEY

被引:25
作者
ROBSON, L [1 ]
HUNTER, M [1 ]
机构
[1] UNIV LEEDS,SCH MED,DEPT PHYSIOL,LEEDS LS2 9NQ,W YORKSHIRE,ENGLAND
来源
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY | 1994年 / 429卷 / 01期
基金
英国惠康基金;
关键词
VOLUME REGULATION; PROXIMAL TUBULE; VOLTAGE DEPENDENCE; CALCIUM;
D O I
10.1007/BF02584035
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Stretch-activated channels (SACs) have been implicated in the control of epithelial cell volume. Such channels are generally sensitive to the trivalent lanthanide, gadolinium (Gd3+). In this study, using Gd3+ sensitivity and volume activation as indices, we have looked for ionic currents attributable to SACs using the whole-cell-patch clamp technique in freshly isolated proximal tubule cells of the frog. Hypotonic shock caused a reversible increase in whole-cell conductance, which was inhibited by Gd3+. In conjunction with this increase in conductance, cell length (measured using an optical technique) also increased. We observed two types of volume- and Gd3+-sensitive currents: voltage-dependent I-VD and voltage-independent I-VI. I-VD was found in all cells, activated by depolarisation and hypotonic shock, and was inhibited reversibly by 10 mu M Gd3+. The conductance did not discriminate between Na+ and K+ but was slightly anion-selective and was Ca2+-permeable. I-IV was observed in only 50% of cells and was also inhibited by Gd3+. Although the inhibition was irreversible, it was dose-dependent, suggesting a specific effect of Gd3+ on I-VI. Cells that showed I-VI had a significantly higher conductance than those that did not (38.7+/-4.4, n=20, and 20.5+/-0.7, n=15, mu S.cm(-2) respectively). In contrast to I-VD, I-VI was mildly cation-selective, Ca2+-permeable, and also selective for Na+ over K+. As with I-VD, volume-induced duced increases in I-VI were inhibited by Gd3+. Both of these currents are activated during hypotonic shock and may be involved in volume-regulatory processes in frog proximal cells.
引用
收藏
页码:98 / 106
页数:9
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