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氨甲酰胆碱通过M_(2)胆碱能受体对大鼠心肌细胞发挥正性肌力作用

崔香丽, 陈还珍, 吴博威

山西医科大学生理学教研室.山西,太原 030001；山西医科大学第一医院心内科.山西,太原 030001

摘要

为研究氨甲酰胆碱(carbachol,CCh)对大鼠心肌细胞的正性肌力作用机制,利用电压钳方法观察CCh对急性分离的单个大鼠心肌细胞L--型钙电流(I_(Ca,L))和钠/钙交换电流(I_(Na/Ca))的影响。细胞负载Fura--2/AM后,用离子成像系统测定场刺激下单个大鼠心肌细胞的钙瞬变和细胞缩短。结果表明,100#mu#mol/L CCh使正向I_(Na/Ca)从(1.18±0.57)pA/pF增加到(1.65±0.52)pA/pF({sl P}<0.01),反向I_(Na/Ca)从(1.11±0.49)pA/pF增加到(1.53±0.52)pA/pF({sl P}<0.01),但不影响I_(Ca,L)。阿托品(非选择性M胆碱受体拮抗剂)和methoctramine(选择性M_(2)胆碱受体拮抗剂)可阻断这种增加作用。100#mu#mol/L CCh使钙瞬变从对照组的203.8±50.0增加到234.8±64.3,使细胞缩短从对照组的(3.00±0.67)#mu#m增加到(3.55±1.21)#mu#m。KB--R7943(选择性反向I_(Na/Ca)抑制剂)不影响钙瞬变和细胞缩短的基础水平,却完全阻断CCh引起的钙瞬变和细胞缩短的增加。尼卡地平(I_(Ca,L)抑制剂)抑制钙瞬变和细胞缩短。CCh在尼卡地平存在下仍可增加钙瞬变和细胞缩短值,提示其正性肌力作用是通过刺激钠/钙交换实现的。CCh不改变钙敏感性。阿托品和methoctramine阻断CCh的这种激动作用,说明CCh的正性肌力作用是通过M_(2)受体实现的。以上结果提示,CCh对大鼠心肌细胞有正性肌力作用,这种作用是通过激动反向钠/钙交换实现,由M_(2)受体介导。

关键词： 氨甲酰胆碱; 毒蕈碱型ACh受体; 钠/钙交换; 钙; methoctramine; 大鼠; fura-2; 成像; 心肌

Carbachol exhibited positive inotropic effect on rat ventricular myocytes via M_(2) muscarinic receptors

Cui Xiangli, Chen Huanzhen, Wu Bowei

Department of physiology, Shanxi Medical University.Taiyuan 030001,Shanxi；Department of Physiology, Shanxi Medical University.Taiyuan 030001,Shanxi；China

Abstract

The present study was aimed to investigate the positive inotropic mechanism of carbachol (CCh) on rat ventricular myocytes. The effects of CCh on L-type calcium current (I_(Ca,L)) and Na~(+)/Ca~(2+) exchange current (I_(Na/Ca)) were investigated in isolated rat ventricular myocytes. After loading myocytes with Fura-2/AM, electrically triggered Ca~(2+) transient and cell shortening in single myocyte were measured simultaneously using ion imaging system with charge-coupled device (CCD) camera. CCh (100 #mu#mol/L)increased I_(Na/Ca) in forward mode from (1.18±0.57) pA/pF in the conrol group to (1.65±0.52) pA/pF (P＜0.01) and that in reverse mode from (1.11±0.49) pA/pF in the control group to (1.53±0.52) pA/pF (P＜0.01), respectively. CCh had no effect on I_(Ca,L). The stimulatory effect of CCh on I_(Na/Ca) was blocked by application of atropine, a non-selective M muscarinic receptor antagonist, and methoctramine,a selective M_(2) muscarinic receptor antagonist. CCh (100 #mu#mol/L) increased cell shortening from (3.00±0.67) #mu#m in the control group to (3.55±1.21) #mu#m. Ca~(2+) transient was also increased from 203.8±50.0 in the control group to 234.8±64.3 in 100 #mu#mol/L CCh group. KB-R7943, a selective inhibitor of reverse mode Na~(+)/Ca~(2+) exchange, did not change the baseline level of cell shortening and Ca~(2+) transient,while completely abolished CCh-induced increments of both Ca~(2+) transient and cell shortening. CCh increased cell shortening and Ca~(2+) transient in the presence of nicardipine, indicating that the positive inotropic effect of CCh was through activation of Na~(+)/Ca~(2+) exchange.Calcium sensitivity was not changed by CCh. Both atropine and methoctramine abolished the positive inotropic effects of CCh,demonstrating that CCh induced positive inotropism via the M_(2) muscarinic receptor. The results suggest that CCh increases cell contraction and Ca~(2+) transient in rat ventricular myocytes. This positive inotropic effect of CCh is through activation of reverse mode Na~(+)/Ca~(2+) exchange, and M_(2) receptors are involved in mediating CCh-induced contraction.

Key words: carbachol;muscarinic acetylcholine receptor;Na/Ca exchange;Calcium;methoctramine;Rat;Fura-2;imaging;Myocardium

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引用本文：

崔香丽, 陈还珍, 吴博威. 氨甲酰胆碱通过M_(2)胆碱能受体对大鼠心肌细胞发挥正性肌力作用[J]. 生理学报 2007; 59 (5): 667-673.

Cui Xiangli, Chen Huanzhen, Wu Bowei. Carbachol exhibited positive inotropic effect on rat ventricular myocytes via M_(2) muscarinic receptors. Acta Physiol Sin 2007; 59 (5): 667-673 (in Chinese with English abstract).