长期应用左旋精氨酸对慢性低氧肺动脉平滑肌细胞钾通道的作用

目的　探讨长期应用左旋精氨酸 (L Arg)对慢性低氧大鼠肺动脉平滑肌细胞 (PASMC)膜钾通道的作用 ,为慢性低氧性肺动脉高压的防治手段提供理论依据。方法　雄性Wistar大鼠 18只 ,每组 6只 ,随机分为三组 :生理盐水对照组 (A组 )、慢性低氧组 (B组 )和慢性低氧 +L Arg组 (C组 )。单个大鼠的PASMC获得采用急性酶分离法 (胶原酶Ⅰ型和木瓜蛋白酶 )。用全细胞膜片钳技术测定三组PASMC的静息膜电位 (Em)、电压门控钾通道 (Kv通道 )电流和钙激活钾通道 (KCa通道 )电流。结果　 (1)B组大鼠PASMC的静息膜电位为 (- 31± 8)mV ,A组为 (- 4 2± 5 )mV ,两组比较差异有显著性 (P <0 0 1)。C组大鼠PASMC的静息膜电位为 (- 39± 4 )mV ,与B组比较差异有显著性 (P <0 0 5 )。(2 )对Kv通道 (在 +5 0mV电压刺激时峰值电流 ) :B组大鼠PASMC的峰值电流为 (6 2± 5 )pA/pF ,A组为 (12 1± 9)pA/pF ,两组比较差异也有显著性 (P <0 0 1)。C组大鼠PASMC的峰值电流为 (95± 3)pA/pF ,与B组比较差异也有显著性 (P <0 0 0 1)。 (3)对KCa通道 (+5 0mV电压刺激时的峰值电流 ) :B组大鼠PASMC的峰值电流为 (74 7± 4 1)pA/pF ,A组为 (5 3 6± 5 9)pA/pF ,两组比较差异有显著性 (P <0 0 5 )。应用L Arg后 ,C组大鼠PASMC的峰值电

The effects of long-term application of L-arginine on K+ channel in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia

OBJECTIVE: To investigate the effects of long-term application of L-arginine (L-Arg) on K(+) channel in pulmonary artery smooth muscle cells (PASMC) from rats exposed to chronic hypoxia. METHODS: Male Wistar rats were randomly divided into three groups: group A (control group), group B (chronic hypoxia group) and group C (chronic hypoxia plus L-Arg treatment group). The rats were exsanguinated and the intrapulmonary arteries (300 approximately 700 OD) were collected. Single PASMC was obtained by the acute enzyme separation method (collagnase Iplus papain) and the conventional whole-cell patch clamp technique was used to record resting membrane potential (Em), potassium ion currents of voltage-gated potassium channel and Ca(2+)-sensitive potassium channel. RESULTS: (1) The Em of group B (-31 +/- 8) mV, n = 6] was significantly higher than that of group A (-42 +/- 5) mV, n = 6, P < 0.01]. After long-term application of L-Arg, the Em of group C (-39 +/- 4) mV, n = 6] was significantly lower than that of group B (P < 0.05). (2) The peak current at +50 mV of voltage-gated potassium channel was compared among three groups. In group B (62.2 +/- 5.3) pA/pF, n = 6], it was significantly lower than that of group A (121 +/- 9) pA/pF, n = 6] (P < 0.01). After long-term application of L-Arg, the peak current at +50 mV of voltage-gated potassium channel in group C (95 +/- 3) pA/pF, n = 6] was significantly higher than that of group B (P < 0.001). (3) The peak current at +50 mV of Ca(2+)-sensitive potassium channel was compared among three groups. In group B (74.7 +/- 4.1) pA/pF, n = 6], it was significantly higher than that of group A (53.6 +/- 5.9) pA/pF, n = 6] (P < 0.05). After long-term application of L-Arg, the peak current at +50 mV of Ca(2+)-sensitive potassium channel in group C (31.8 +/- 1.8) pA/pF, n = 6] was significantly lower than that of group B (74.7 +/- 4.1) pA/pF, n = 6] (P < 0.001). CONCLUSIONS: The long-term application of L-Arg can improve the resting membrane potential of PASMCs from rats exposed to chronic hypoxia, increase the currents of voltage-gated potassium channel and decrease the currents of Ca(2+)-sensitive potassium channel. These effects are considered to be effective in improving chronic hypoxic pulmonary hypertension.