Li H Y, Quamme G A
Department of Medicine, University of British Columbia, Vancouver Hospital, Canada.
Biochim Biophys Acta. 1997 Jan 10;1355(1):61-8. doi: 10.1016/s0167-4889(96)00117-6.
Caffeine has been extensively used to study intracellular Ca2+ control and contraction-relaxation in cardiomyocytes. The effects of caffeine on intracellular free Mg2+ concentration, [Mg2+]i, were studied in isolated adult rat ventricular myocytes by fluorescent techniques using mag-fura-2. Basal [Mg2+]i was 0.62 +/- 0.02 mM, n = 54, in quiescent cells and 0.73 +/- 0.02 mM, n = 23, in electrically-stimulated adult rat ventricular myocytes. Caffeine, 20 mM, significantly decreased [Mg2+] in both quiescent (-0.17 +/- 0.01 mM) and electrically-stimulated (-0.16 +/- 0.01 mM) adult ventricular myocytes. Ryanodine, a blocker for Ca(2+)-release channels of the sarcoplasmic reticulum, did not have any effect on basal [Mg2+]i, 0.67 +/- 0.02 mM nor on caffeine-induced reduction in [Mg2+]i, -0.16 +/- 0.01 mM in quiescent cardiomyocytes or electrically-stimulated cells; 0.74 +/- 0.03 mM and -0.11 +/- 0.03 mM, respectively. Ruthenium red, an inhibitor of mitochondrial Ca2+ uptake, also failed to alter basal [Mg2+]i, or caffeine-induced reduction in [Mg2+], in either quiescent or electrically-stimulated cells. The effects of caffeine on [Mg2+]i, may be important in considering the use of this drug to study contraction/function studies in heart cells.
咖啡因已被广泛用于研究心肌细胞内的钙离子控制及收缩-舒张过程。利用镁荧光指示剂fura-2，通过荧光技术在分离的成年大鼠心室肌细胞中研究了咖啡因对细胞内游离镁离子浓度（[Mg2+]i）的影响。静息细胞的基础[Mg2+]i为0.62±0.02 mM（n = 54），电刺激的成年大鼠心室肌细胞的基础[Mg2+]i为0.73±0.02 mM（n = 23）。20 mM的咖啡因可使静息成年心室肌细胞（-0.17±0.01 mM）和电刺激成年心室肌细胞（-0.16±0.01 mM）中的[Mg2+]显著降低。兰尼碱是肌浆网钙释放通道的阻滞剂，对静息心肌细胞或电刺激细胞的基础[Mg2+]i（0.67±0.02 mM）以及咖啡因诱导的[Mg2+]i降低（分别为-0.16±0.01 mM和-0.11±0.03 mM）均无影响。线粒体钙摄取抑制剂钌红也未能改变静息或电刺激细胞中的基础[Mg2+]i或咖啡因诱导的[Mg2+]降低。咖啡因对[Mg2+]i的影响在考虑使用该药物研究心脏细胞的收缩/功能时可能具有重要意义。
