Different types of Ca2+ channels in mammalian skeletal muscle cells in culture.
This paper describes the existence of two pharmacologically distinct types of Ca2+ channels in rat skeletal muscle cells (myoballs) in culture. The first class of Ca2+ channels is insensitive to the dihydropyridine (DHP) (+)-PN 200-110; the second class of Ca2+ channels is blocked by low concentrations of (+)-PN 200-110. The two pharmacologically different Ca2+ channels are also different in their voltage and time dependence. The threshold for activation of the DHP-insensitive Ca2+ channel is near -65 mV, whereas the threshold for activation of the DHP-sensitive Ca2+ channel is near -30 mV. Current flowing through the DHP-insensitive Ca2+ channel is transient with relatively fast kinetics. Half-maximal inactivation for the DHP-insensitive Ca2+ channel is observed at a holding potential Vh0.5 = -78 mV and the channel is completely inactivated at -60 mV. Two different behaviors have been found for DHP-sensitive channels with two different kinetics of inactivation (one being about 16 times faster than the other at -2 mV) and two different voltage dependencies. These two different behaviors are often observed in the same myoball and may correspond to two different subtypes of DHP-sensitive Ca2+ channels or to two different modes of expression of one single Ca2+ channel protein.
Cognard
C
C
Lazdunski
M
M
Romey
G
G
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D003035:Cobalt / Q000494:pharmacology; D004095:Dihydropyridines; D004553:Electric Conductivity; D007473:Ion Channels / Q000145:classification* / Q000187:drug effects; D008564:Membrane Potentials; D009132:Muscles / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D013779:Tetrodotoxin / Q000494:pharmacology
D004095:Dihydropyridines; D007473:Ion Channels; D011725:Pyridines; D001464:Barium; D003035:Cobalt; D013779:Tetrodotoxin; C038806:1,4-dihydropyridine; D002118:Calcium