Pharmacological properties of two types of calcium channel in embryonic chick skeletal muscle cells in culture.
We have studied the effects of organic and inorganic Ca channel blockers on the two-component action potentials (low- and high-threshold components) in cultured chick skeletal muscle cells, which are generated by the T- and L-type voltage-dependent Ca channels (VDCCs), respectively. Nifedipine and D600 effectively blocked the high-threshold component of the action potential, whereas omega-conotoxin and phenytoin had no effect on this component. By contrast, the low-threshold component was insensitive to all of these organic Ca channel blockers. Blocking effects of polyvalent cations were observed with the following rank order of relative potency (mean apparent dissociation constant in microM): La3+ (14.7) greater than Ni2+ (20.7) greater than Cd2+ (51.2) greater than Co2+ (912) for the low-threshold component, and Cd2+ (0.7) greater than La3+ (29.2) greater than Co2+ (431) greater than Ni2+ (1241) for the high-threshold component. Taken together, these findings suggest that the pharmacological properties of the T- and L-type VDCCs in cultured chick skeletal muscle cells may differ from those in other preparations.
Satoh
R
R
Department of Physiology, Kitasato University School of Medicine, Kanagawa, Japan.
Nakabayashi
Y
Y
Kano
M
M
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002412:Cations; D002478:Cells, Cultured; D002642:Chick Embryo; D005711:Gallopamil / Q000494:pharmacology; D007700:Kinetics; D008978:Mollusk Venoms / Q000494:pharmacology; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010672:Phenytoin / Q000494:pharmacology; D020960:omega-Conotoxins
D015220:Calcium Channels; D002412:Cations; D008978:Mollusk Venoms; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; C053423:Conus magus toxin; D005711:Gallopamil; D010672:Phenytoin; D009543:Nifedipine