Ca2+ regulated K+ and nonselective cation channels in the basolateral membrane of rat colonic crypt base cells

被引:78
作者
Bleich, M
Riedemann, N
Warth, R
Kerstan, D
Leipziger, J
Hor, M
VanDriessche, W
Greger, R
机构
[1] UNIV FREIBURG,INST PHYSIOL,D-79104 FREIBURG,GERMANY
[2] CATHOLIC UNIV LEUVEN,PHYSIOL LAB,B-3000 LOUVAIN,BELGIUM
来源
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY | 1996年 / 432卷 / 06期
关键词
Cl-; secretion; carbachol K+ channel; cAMP; exocrine secretion; non-selective cation channel; channel;
D O I
10.1007/s004240050229
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
We have previously shown that a new type of K+ channel, present in the basolateral membrane of the colonic crypt base (blm), is necessary for cAMP-activated Cl- secretion. Under basal conditions, and when stimulated by carbachol (CCH) alone, this channel is absent. In the present patch clamp-study we examined the ion channels present in the blm under cell-attached and in cell-excised conditions. In cell-attached recordings with NaCl-type solution in the pipette we measured activity of a K+ channel of 16 +/- 0.3 pS (n = 168). The activity of this channel was sharply increased by CCH (0.1 mmol/l, n = 26). Reduction of extracellular Ca2+ to 0.1 mmol/l (n = 34) led to a reversible reduction of activity of this small channel (SKCa). It was also inactivated by forskolin (5 mu mol/l, n = 38), whilst the K+ channel noise caused by the very small K+ channel increased. Activity of non-selective cation channels (NScat) was rarely observed immediately prior to the loss of attached basolateral patches and routinely in excised patches. The NScat, with a mean conductance of 49 +/- 1.0 pS (n = 96), was Ca2+ activated and required >10 mu mol/l Ca2+ (cytosolic side = cs). It was reversibly inhibited by ATP (<1 mmol/l, n = 13) and by 3',5-dichloro-diphenylamine-2-carboxylate (10-100 mu mol/l, n = 5). SKCa was also Ca2+ dependent in excised inside-out basolateral patches. Its activity stayed almost unaltered down to 1 mu mol/l (cs) and then fell sharply to almost zero at 0.1 mu mol/l Ca2+ (cs, n = 12). SKCa was inhibited by Ba2+ (n = 31) and was charybdotoxin sensitive (1 nmol/l) in outside-out ba solateral patches (n = 3). Measurements of the Ca2+ activity ([Ca2+](i)) in these cells using fura-2 indicated that forskolin and depolarization, induced by an increase in bath K+ concentration to 30 mmol/l, reduced [Ca2+](i) markedly (n = 8-10). Hyperpolarization had the opposite effect. The present data indicate that the blm of these cells contains a small-conductance Ca2+-sensitive K+ channel. This channel is activated promptly by very small increments in [Ca2+](i) and is inactivated by a fall in[Ca2+](i) induced by forskolin.
引用
收藏
页码:1011 / 1022
页数:12
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