Developmental Changes of Ni²⁺ Sensitivity and Automaticity in Nkx2.5-Positive Cardiac Precursor Cells From Murine Embryonic Stem Cell

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Background It is controversial which subtypes of T type Ca²⁺ channels are implicated in automaticity of cardiac cells during the embryonic period.Method and Results The effect of Ni²⁺ on the automaticity of Nkx2.5-positive cardiac precursor cells sorted from embryonic stem cells during their differentiation was examined using patch clamp techniques. Although 40μmol/L Ni²⁺, which is enough to block Ni²⁺sensitive T type-Ca²⁺ channels, decreased the spontaneous beating rate in all cells in the early and intermediate stage, Ni²⁺ did not show any effects on the automaticity of 50% of the cells in the late stage. Conclusion These results indicate that Ni²⁺-sensitive T-type Ca²⁺ channels expressed in the Nkx2.5-positive cardiac precursor cells are developmentally regulated. (Circ J 2004; 68: 724 - 726)