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目的 观察急性缺氧对豚鼠肠系膜动脉平滑肌细胞电生理特性的影响.方法 直径＜100 μm的豚鼠肠系膜动脉进一步去除结缔组织后,应用全细胞膜片钳技术观察急性缺氧对微动脉段上平滑肌细胞膜电流、膜电位、膜电容、膜电导或膜电阻的影响.结果当钳制电压为-40 mV时,急性缺氧引起一个反应幅度(76 ±23)pA的外向电流,细胞静息膜电位从(-22.5±1.2)mV超级化到(-42.0 ±2.8)mV(P ＜0.01).急性缺氧可以电压依赖地增强细胞外向电流,且主要增强0～+40 mV电压区间的电流,激活电流幅度0 mV时从(140±18)pA增加到(660±124)pA(P ＜0.01),+20 mV时从(282±23)pA增加到(1120±186)pA(P ＜0.01),+40 mV时从(423±40)pA增加到(1800±275)pA(P ＜0.01).背景灌流1 mmol/L大电导Ca2+激活K+通道(BKca)阻断剂四乙胺后,这一增强作用显著减弱.急性缺氧使细胞膜电阻从(446 ±55)MΩ增加到(2187±290)MΩ(P＜0.01),膜电容从(184.3±75.0)pF减少至(17.6±2.2)pF(P＜0.01).联合应用30 μmoL/L缝隙连接阻断剂18β-甘草次酸和10 mmol/L四乙胺后,急性缺氧对细胞膜电流的影响基本消失.结论 急性缺氧通过激活肠系膜动脉平滑肌细胞膜上BKca通道,引起K+外流,细胞超极化,血管舒张,保证肠系膜微循环的血液供应.同时通过抑制细胞间缝隙连接使其产生的伤害信息局限化.

Objective To observe the effects of acute hypoxia on the electrophysiological properties of vascular smooth muscle cells(VSMCs)of mesenteric artery in guinea pig.Methods A segment of mesenteric artery(MA)(outer diameter ＜ 100 μm)of guinea pig was digested with collagenase A and its adventitial connective tissue cleaned subsequently with fine tweezers.Whole-cell patch clamp recordings were performed to study the effects of acute hypoxia on the whole-cell membrane current,resting membrane potential(RP),membrane input capacitance(Cinput),and membrane input resistance(Rinput or its reciprocal membrane input conductance Ginput)of VSMC embedded in arteriolar segment.Results Acute hypoxia induced an outward current with an amplitude of(76 ± 23)pA at holding potential-40 mV and hyperpolarizated VSMC from a RP of(-22.5 ± 1.2)mV to(-42.0 ± 2.8)mV(P ＜ 0.01).Acute hypoxia increased the outward current of VSMC in a voltage-dependent manner.And this enhancement was more pronounced at potentials from 0 to + 40 mV.The whole-cell membrane current of VSMC induced by step commands(0,+ 20 and + 40 mY)increased from(140 ± 18)pA to(660 ± 124)pA(P ＜ 0.01),(282±23)pA to(1120 ±186)pA(P＜0.01)and(423 ±40)pA to(1800 ±275)pA(P＜0.01)respectively.In the presence of 1 mmol/L tetraethylammonium(TEA,a large conductance Ca2+-activated K+ channel blocker),the enhancement of VSMC membrane current by acute hypoxia was significantly reduced.Acute hypoxia increased the Rimput of VSMC in MA from(446 ±55)MΩ to(2187 ±290)MΩ(P＜0.01)and deereased the Cinput from(184.3 ±75.0)pF to(17.6 ±2.2)pF(P＜0.01).In the presence of 30 μmoL/L 18β-glycyrrhetinic acid(18βGA,a gap junction blocker)and 10 mmol/L TEA,the effects of acute hypoxia on the membrane current of VSMCs were almost abolished.Conclusion Acute hypoxia causes vascular hyperpolarization and vasodilation by activating large conductance Ca2+-activated K + channels of VSMC and inhibits gap junctions between VSMCs so as to improve microcirculation and localize hypoxia-induced damage.