Polarized distribution of L-type calcium channels in early sea urchin embryos.
Using the whole cell clamp technique, we have measured calcium-dependent currents and steady-state conductance in early sea urchin blastomeres. The calcium currents in M phase decreased from 8.5 microA/cm2 at the four-cell stage to 5.4 microA/cm2 at the eight-cell stage. In 16-cell stage embryos, calcium currents were 7.4 microA/cm2 in the mesomeres, 2.3 microA/cm2 in the macromeres, and were not detected in the micromeres. In contrast, the micromeres had a two- to threefold higher steady-state conductance than the mesomeres or macromeres, which may be due to potassium ion conductivity. Nifedipine, an L-type channel antagonist, delays cleavage division at a concentration of 0.05-0.1 mM and causes developmental defects, such as poor skeletal differentiation in later sea urchin embryos.
Dale
B
B
Stazione Zoologica, Naples, Italy.
Yazaki
I
I
Tosti
E
E
D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D020746:Calcium Channels, L-Type; D002455:Cell Division / Q000187:drug effects; D016764:Cell Polarity; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005775:Gastrula / Q000166:cytology / Q000502:physiology; D008855:Microscopy, Electron, Scanning; D009543:Nifedipine / Q000494:pharmacology; D015221:Potassium Channels / Q000494:pharmacology; D012617:Sea Urchins / Q000196:embryology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D015221:Potassium Channels; D009543:Nifedipine; D002118:Calcium