Ca2+ channel activities in the limb bud of early embryonic chick.

Ca2+ channel activities were recorded in the limb bud of embryonic day 4 chick with Ca2+ sensitive fluorescence (Fura-2) measurements and patch clamp techniques. Rises in intracellular Ca2+ concentrations were evoked by depolarization with the application of 100 mM K+ and this Ca2+ response was abolished by removing extracellular Ca2+. The Ca2+ response was blocked by 10 microM nifedipine and enhanced by 5 microM Bay K 8644. Long-lasting inward currents were revealed by whole-cell patch clamp recordings from dissociated cells of the limb bud. The inward current was also blocked by 10 microM nifedipine. Our study suggested the presence of L-type Ca2+ channels in the limb bud cells.