Background: It is controversial which subtypes of T type Ca(2+) channels are implicated in automaticity of cardiac cells during the embryonic period.
Method and results: The effect of Ni(2+) 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 40 micromol/L Ni(2+), which is enough to block Ni(2+)sensitive T type-Ca(2+) channels, decreased the spontaneous beating rate in all cells in the early and intermediate stage, Ni(2+) did not show any effects on the automaticity of 50% of the cells in the late stage.
Conclusion: These results indicate that Ni(2+)-sensitive T-type Ca(2+) channels expressed in the Nkx2.5-positive cardiac precursor cells are developmentally regulated.