CAJ | 학술논문

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(ICa,L)和钠/钙交换电流(INa/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 μmol/L CCh使正向INa/Ca从(1.18±0.57)pA/pF增加到(1.65±0.52)pA/pF(P＜O.01),反向INa/Ca从(1.11±0.49)pA/pF增加到(1.53±0.52)pA/pF(P＜0.01),但不影响ICa,L.阿托品(非选择性M胆碱受体拮抗剂)和methoctramine(选择性M2胆碱受体拮抗剂)可阻断这种增加作用.100 μmol/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)μm增加到(3.55±1.21)μm.KB-R7943(选择性反向INa/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(ICa,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M2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M2受体介导.
위연구안갑선담감(carbachol,CCh)대대서심기세포적정성기력작용궤제,이용전압겸방법관찰CCh대급성분리적단개대서심기세포L-형개전류(ICa,L)화납/개교환전류(INa/Ca)적영향.세포부재Fura-2/AM후,용리자성상계통측정장자격하단개대서심기세포적개순변화세포축단.결과표명,100 μmol/L CCh사정향INa/Ca종(1.18±0.57)pA/pF증가도(1.65±0.52)pA/pF(P＜O.01),반향INa/Ca종(1.11±0.49)pA/pF증가도(1.53±0.52)pA/pF(P＜0.01),단불영향ICa,L.아탁품(비선택성M담감수체길항제)화methoctramine(선택성M2담감수체길항제)가조단저충증가작용.100 μmol/L CCh사개순변종대조조적203.8±50.0증가도234.8±64.3,사세포축단종대조조적(3.00±0.67)μm증가도(3.55±1.21)μm.KB-R7943(선택성반향INa/Ca억제제)불영향개순변화세포축단적기출수평,각완전조단CCh인기적개순변화세포축단적증가.니잡지평(ICa,L억제제)억제개순변화세포축단.CCh재니잡지평존재하잉가증가개순변화세포축단치,제시기정성기력작용시통과자격납/개교환실현적.CCh불개변개민감성.아탁품화methoctramine조단CCh적저충격동작용,설명CCh적정성기력작용시통과M2수체실현적.이상결과제시,CCh대대서심기세포유정성기력작용,저충작용시통과격동반향납/개교환실현,유M2수체개도.
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 (ICa,L) and Na+/Ca2+ exchange current (INa/Ca) were investigated in isolated rat ventricular myocytes. After loading myocytes with Fura-2/AM, electrically triggered Ca2+ transient and cell shortening in single myocyte were measured simultaneously using ion imaging system with charge-coupled device (CCD) camera. CCh (100 μmol/L)increased INa/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 ICa,L. The stimulatory effect of CCh on INa/Ca was blocked by application of atropine, a non-selective M muscarinic receptor antagonist, and methoctramine,a selective M2 muscarinic receptor antagonist. CCh (100 μmol/L) increased cell shortening from (3.00±0.67) μm in the control group to (3.55±1.21) μm. Ca2+ transient was also increased from 203.8±50.0 in the control group to 234.8±64.3 in 100 μmol/L CCh group. KBR7943, a selective inhibitor of reverse mode Na+/Ca2+ exchange, did not change the baseline level of cell shortening and Ca2+ transient,while completely abolished CCh-induced increments of both Ca2+ transient and cell shortening. CCh increased cell shortening and Ca2+transient in the presence of nicardipine, indicating that the positive inotropic effect of CCh was through activation of Na+/Ca2+ 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 M2 muscarinic receptor. The results suggest that CCh increases cell contraction and Ca2+ transient in rat ventricular myocytes. This positive inotropic effect of CCh is through activation of reverse mode Na+/Ca2+ exchange, and M2 receptors are involved in mediating CCh-induced contraction.