抄録
Mouse embryonic stem (mES) cells have abilities to differentiate into various types of the cells, including cardiomyocytes. In this study we examined Ca2+ signaling pathways in mES cells for excitation-contraction (E-C) coupling during the differentiation into cardiomyocytes. To identify the cardiac precursor cells, we used the mES cells transfected with the vector containing GFP driven by mouse cardiac α-actin promoter. Caffeine effects on [Ca2+]i were observed in GFP-positive precursor cells cultured for longer than 5 days without leukemia inhibitory factor and these effects increased during the differentiation. A depolarization induced elevation of [Ca2+]i was observed in 10%, 13%, 25% and 46% of 4-day, 5-7 day, 12-14 day and 24-27 day differentiated cells, respectively. In whole cell patch clamp experiments, T-type but not L-type Ca2+ currents could be recorded in the precursor cells at 12-day stages. In 19-day or beating cells, L-type Ca2+ currents were observed. The expressions of mRNAs for RyR2 and T-type Ca2+ channel were detected from 4-day differentiated cells, but mRNAs for L-type Ca2+ channel could be detected from 7-day differentiated cells. The expression levels of these genes increased during the differentiation. From these results we conclude that main Ca2+ entry pathways switch from T-type Ca2+ channel to L-type one during the differentiation, which might contribute to E-C coupling. [Jpn J Physiol 54 Suppl:S103 (2004)]
