Rat skeletal muscle cells in culture possess two pharmacologically distinct types of voltage-sensitive Ca2+ channels: a DHP-insensitive channel activated at low potentials and a DHP-sensitive channel.
The study identifies two distinct classes of calcium channels in rat skeletal muscle cells with different pharmacological sensitivities and electrophysiological properties.
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 et al. (Wed,) conducted a other in In vitro rat skeletal muscle cells. (+)-PN200-110 vs. Control (absence of drug) was evaluated on Identification of Ca2+ channel types based on DHP sensitivity and voltage dependence. Rat skeletal muscle cells in culture possess two pharmacologically distinct types of voltage-sensitive Ca2+ channels: a DHP-insensitive channel activated at low potentials and a DHP-sensitive channel.