鸡直肠纵肌对外源性ATP的膜电流反应。

Membrane current responses to externally-applied ATP in the longitudinal muscle of the chicken rectum.

作者信息

Matsuoka T, Komori S, Ohashi H

机构信息

Department of Veterinary Science, Faculty of Agriculture, Gifu University, Japan.

出版信息

Br J Pharmacol. 1993 Sep;110(1):87-94. doi: 10.1111/j.1476-5381.1993.tb13775.x.

DOI:10.1111/j.1476-5381.1993.tb13775.x

PMID:8220917

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC2176010/

Abstract

Membrane current responses to ATP in enzymically-dispersed single smooth muscle cells from the chicken rectum were investigated by the whole-cell voltage clamp technique. 2. In cells dialysed with a KCl-rich solution under voltage clamp at a holding potential of -40 mV, ATP (10 microM) produced an inward current followed by an outward current. When the holding potential was changed to 0 mV and -80 mV, the biphasic current response to ATP was converted to an outward current alone and an inward current alone, respectively. 3. External application of tetraethylammonium (TEA, 5 mM), intracellular dialysis with a CsCl-rich solution, or inclusion of EGTA (10 mM) in the pipette abolished the outward current response to ATP. 4. Neither depletion of Ca2+ store with caffeine (10 mM) nor block of voltage-gated Ca2+ channels with nifedipine (10 microM) affected the biphasic current response to ATP. After removal of the extracellular Ca2+ the outward current response to ATP was abolished. 5. alpha,beta-methylene ATP (100 microM) elicited a current similar to the ATP-induced current. In the presence of alpha,beta-methylene ATP (100 microM), application of ATP (100 microM) was without effect. 6. In CsCl-filled cells, ATP analogues elicited an inward current and the order of potency was ATP not equal to alpha, beta-methylene ATP > ADP >> AMP. 7. Inclusion of GTP gamma S (0.2 mM) or GDP beta S (2 mM) in the pipette did not affect the ATP-induced inward current in CsCl-filled cells. The reversal potential of the ATP-induced inward current was about 0 mV and was completely inhibited after replacement of the cations in the bath solution by Tris. The reversal potential remained almost unchanged after replacement of Na+ in the bath solution with 1 10 mM Ca2+, but shifted in the negative direction after replacement of Na+ or both Na+ and Ca2+ with glucosamine.8. The results suggest that ATP acts on P2 purinoceptors to cause activation of cation channels with selectivity for Ca2+ over Na+. Moreover, it appears that no G-protein-mediated mechanism is involved and increased Ca2+ entry through the cation channels causes activation of Ca2+-activated K+ channels.

摘要

采用全细胞膜片钳技术研究了鸡直肠酶解分散的单个平滑肌细胞对ATP的膜电流反应。2. 在-40 mV的钳制电位下，用富含KCl的溶液透析细胞时，ATP（10 μM）产生内向电流，随后是外向电流。当钳制电位变为0 mV和-80 mV时，对ATP的双相电流反应分别转变为仅外向电流和仅内向电流。3. 细胞外施加四乙铵（TEA，5 mM）、用富含CsCl的溶液进行细胞内透析或移液管中加入EGTA（10 mM）均可消除对ATP的外向电流反应。4. 用咖啡因（10 mM）耗尽Ca2+储存或用硝苯地平（10 μM）阻断电压门控Ca2+通道均不影响对ATP的双相电流反应。去除细胞外Ca2+后，对ATP的外向电流反应消失。5. α,β-亚甲基ATP（100 μM）引发的电流与ATP诱导的电流相似。在存在α,β-亚甲基ATP（100 μM）的情况下，施加ATP（100 μM）无效。6. 在充满CsCl的细胞中，ATP类似物引发内向电流，其效力顺序为ATP不等于α,β-亚甲基ATP＞ADP＞＞AMP。7. 移液管中加入GTPγS（0.2 mM）或GDPβS（2 mM）不影响充满CsCl的细胞中ATP诱导的内向电流。ATP诱导的内向电流的反转电位约为0 mV，在用Tris替换浴液中的阳离子后完全被抑制。用1 10 mM Ca2+替换浴液中的Na+后，反转电位几乎不变，但在用葡糖胺替换Na+或同时替换Na+和Ca2+后，反转电位向负方向移动。8. 结果表明，ATP作用于P2嘌呤受体，导致对Ca2+选择性高于Na+的阳离子通道激活。此外，似乎不涉及G蛋白介导的机制，通过阳离子通道增加的Ca2+内流导致Ca2+激活的K+通道激活。