Gomez J P, Potreau D
Laboratory of General Physiology, Faculty of Sciences, Poitiers, France.
J Cardiovasc Pharmacol. 1996 Mar;27(3):335-46. doi: 10.1097/00005344-199603000-00005.
The effects of specific inhibitors of sarcoplasmic reticulum (SR) calcium ATPase, thapsigargin (TG), and cyclopiazonic acid (CPA) were investigated on the resting and transient levels of intracellular free calcium concentrations recorded in Indo-1-loaded ventricular myocytes of newborn rat heart in primary culture. The calcium transients were induced by caffeine (10 mM) or high potassium (100 mM) solutions. In 2 day- as in 7-day-old cultured cells, the calcium transients induced by 10 mM caffeine were blocked dose dependently by TG and CPA. The dose-response curves suggest that TG was more efficient than CPA and that both drugs were more efficient in 7-day- than in 2-day-old cells. The calcium transients induced by 100 mM K+ were also strongly inhibited by these agents. The lack of effect on sarcolemmal calcium currents, as shown by whole-cell patch-clamp experiments, suggests that these drugs affect only SR function. In cells exhibiting spontaneous activity, the associated calcium transients were not affected by TG or CPA at the beginning of the culture (2-day-old cells) but were fully blocked at the end (7-day-old cells). These results confirm that TG and CPA specifically inhibit the cardiac SR Ca2+ pump without affecting the sarcolemmal calcium current. Their blocking effect of the calcium transients as a function of the developmental stage of neonatal cardiac cells in culture suggests an increasing role of the SR in the regulation of intracellular calcium. This argues for developmental changes of the SR through the differentiation and maturation of newborn cardiomyocytes at the early stage of the postnatal life, leading to a predominant role of the SR in excitation-contraction coupling mechanisms in adult cells.
研究了肌浆网（SR）钙ATP酶特异性抑制剂毒胡萝卜素（TG）和环匹阿尼酸（CPA）对原代培养的新生大鼠心脏Indo-1标记心室肌细胞中记录的细胞内游离钙浓度的静息水平和瞬时水平的影响。钙瞬变由咖啡因（10 mM）或高钾（100 mM）溶液诱导。在培养2天和7天的细胞中，10 mM咖啡因诱导的钙瞬变被TG和CPA剂量依赖性阻断。剂量反应曲线表明，TG比CPA更有效，且两种药物在7天龄细胞中比在2天龄细胞中更有效。100 mM K+诱导的钙瞬变也被这些药物强烈抑制。全细胞膜片钳实验显示这些药物对肌膜钙电流无影响，表明它们仅影响SR功能。在表现出自发活动的细胞中，相关的钙瞬变在培养开始时（2天龄细胞）不受TG或CPA影响，但在培养结束时（7天龄细胞）被完全阻断。这些结果证实，TG和CPA特异性抑制心脏SR Ca2+泵，而不影响肌膜钙电流。它们对培养的新生心脏细胞发育阶段的钙瞬变的阻断作用表明，SR在细胞内钙调节中的作用日益增强。这表明在出生后早期，随着新生心肌细胞的分化和成熟，SR发生了发育变化，导致SR在成年细胞的兴奋-收缩偶联机制中起主要作用。
