钙三醇干预甲状旁腺素诱导的心肌细胞内钙超载和细胞肥大

目的探讨甲状旁腺素（PTH）对鼠心肌细胞内游离钙（[Ca^2＋]i）和心肌肥大的影响及其机制，以及钙三醇的干预作用。方法培养的新生大鼠心肌细胞以Fluo-3／AM负载，通过激光共聚焦显微术（LSCM）测定细胞内[Ca^2＋]i；以细胞面积和细胞蛋白含量作为心肌细胞肥大指标，体外实验观察PTH瞬时和持续刺激对鼠心肌细胞[Ca^2＋]i和肥大的影响，以及钙三醇的干预作用。结果①在细胞外Ca^2＋为2．5mmol／L时，PTH1-34在0．1和1μmol浓度下的刺激可促使心肌细胞静息[Ca^2＋]i荧光强度（FI）快速上升；1μmol浓度PTH1-34刺激，在细胞外液无钙，或应用10μmol硝苯地平预处理时，心肌细胞静息钙则无明显上升。②培养的心肌细胞应用PTH1-34 0．01和0．1μmol刺激7天后，心肌细胞内钙荧光强度、心肌细胞面积和蛋白含量均较对照组显著增加。若以PTH1-34 0．1μmol刺激，并同时加入0．001μmol的钙三醇干预，上述指标明显降低（P〈0．01）；但应用0．1μmol高浓度钙三醇干预，上述指标则未见显著改善。结论PTH1-34刺激可显著增加培养心肌细胞[Ca^2＋]i，诱导细胞肥大；适宜浓度钙三醇具有保护作用，电压依赖型钙通道的开放引起的细胞外钙内流增加是PTH1-34诱导上述变化的重要机制之一。

Protective roles of calcitriol on overload of intracellular calcium and hypertrophy of cardiomyocytes induced by parathyroid hormone

Objective To observe the effects of calcitriol on intracellular calcium concentration （[Ca^2＋]i） and hypertrophy of cardiomyocytes induced by parathyroid hormone （PTH）. Materials and Methods Cultured neonatal rat cardiomyocytes were loaded with Fluo-3/AM, and [Ca^2＋]i was determined by a laser confocal microscope. Hypertrophic response of neonatal rat cardiomyocytes was assayed by measuring cell surface area and protein content. Results （a） When the extracellular Ca^2＋ was 2.5mmol/L, rapid stimulation of PTH1-34 at the concentration of 0.1 and 1 umol/L significantly elevated fluorescence intensity of [Ca2 ＋]i in cardiomyocytes （P 〈 0.01）. However, when the extracellular fluid contained no calcium or the cardiomyocytes were pre-treated with 10umol/L nifedipine, 1 umol/L PTH1-34 did not induce the increase of fluorescence intensity any more. （b） When the cardiomyocytes were treated in 0.01 and 0.1 umol/L PTH1-34 for 7 days, their surface area, protein content and [Ca^2＋]i increased significantly, especially those treated in 0.1 umol/L PTH1-34. If the cells were co-treated with 0.001 lumol/L calcitriol and 0.1umol.L-1 PTH1 34, their surface area, protein content and [Ca^2＋]i attenuated significantly. However, when the calcitriol concentration increased to 0.1 umol/L in the co-treatment experiment, these changes remained. Conclusion Cardiomyocyte hypertrophy was induced by PTH1-34, and was inhibited by appropriate concentration of calcitriol. Calcium influx through voltage-dependent channel induced by PTH may be one of the important mecha- nisms leading to cardiomyocyte hypertrophy.