L-type Ca2+ currents in ascidian eggs.
We have studied Ca2+ currents in ascidian eggs using the whole-cell clamp technique. T and L components, as observed in somatic cells, are present and the L-type current predominates. Since the IV relationship for these inward currents overlap at -30 mV, separation of the two components using different voltage regimes is not feasible. Increasing external Ca2+ results in larger currents. The L-type current decreases in a dose-dependent fashion in the presence of Mn2+ and Nifedipine, while the T-type current is inhibited in Ni2+. When Ba2+ was used as the carrier ion, channel kinetics and conductance were completely altered. Considering the density and kinetics of L-type channels in unfertilized eggs it is probable they play an important role in regulating cytosolic Ca2+ during early developmental processes.
Dale
B
B
Stazione Zoologica, Villa communale, Naples, Italy.
Talevi
R
R
DeFelice
L J
LJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D004553:Electric Conductivity; D008564:Membrane Potentials / Q000502:physiology; D009865:Oocytes / Q000378:metabolism; D014561:Urochordata / Q000378:metabolism*
D015220:Calcium Channels; D002118:Calcium