三磷酸肌醇信号途径参与血小板激活因子诱导豚鼠心室肌细胞钙浓度增高

目的观察血小板激活因子(PAF)是否影响心室肌细胞钙离子浓度(Ca~(2+)]i)以及通过哪条信号转导通路起作用。方法采用酶法分离豚鼠心室肌细胞,用PAF刺激细胞;用Fluo-3/AM和共聚焦显微镜观察细胞Ca~(2+)]i;用2-氨乙基硼酸二苯酯(2-APB)和雷诺定(ryanodine)分别阻断IP3和雷诺定信号通路。全细胞膜片钳技术观察心室肌细胞L型钙电流(ICa-L)。结果无论在有钙还是无钙台氏液,PAF(1pmol·L-1~10nmol·L-1)都能增加心肌细胞Ca~(2+)]i,其作用能够被2-APB2μmo·lL-1阻断,而不能被雷诺定200μmol·L-1阻断。PAF1nmol·L-1对ICa-L没有明显影响,对照组和实验组电流密度分别为-(11.0±1.9)和-(10.5±1.3)pA·pF-1。结论PAF能增加豚鼠心室肌细胞Ca~(2+)]i,IP3信号通路可能参与了这一过程。

Increasing cytosolic calcium in ventricular myocytes of guinea pig induced by platelet activating factor through inositol 1,4,5-trisphosphate pathway

AIM To observe whether platelet activating factor (PAF) will influence cytosolic calcium concentration (［Ca²⁺］_i) in ventricular myocytes and which signaling pathway is involoved. METHODS Ventricular myocytes were isolated enzymatically. Cells were stimulated with PAF, and ［Ca²⁺］_i was measured with calcium indicator Fluo-3/AM and a confocal laser microscope. For the observation of signaling channel mediated by inositol 1,4,5-trisphosphate (IP₃) and ryanodine, 2-aminoethyl diphenylborate (2-APB, 2 μmol·L^-1) and ryanodine (200 μmol·L^-1) were used respectively for blocking the signaling channel. Whole-cell patch clamp was used to study the effect of PAF on L-type calcium channel (I_Ca-L). RESULTS PAF (1 pmol·L^-1-10 nmol·L^-1) increased ［Ca²⁺］_i in Tyrode′s solution with or without calcium, and the effect was inhibited by 2-APB, but not by ryanodine. I_Ca-L was not changed by PAF 1 nmol·L^-1〔-(11.0±1.9) vs -(10.5±1.3) pA·pF^-1〕. CONCLUSION Increasing ［Ca²⁺］_i of cardiomyocytes induced by PAF is associated with IP3 pathway, but has nothing to do with I_Ca-L and ryanodine pathway.