Effects of ethanol on electrophysiological properties of rat skeletal myotubes in culture

Ethanol was studied for its effects on electrophysiological properties of cultured skeletal myotubes prepared from fetal or neonatal rats. Intracellular recordings were made with KCl-filled (3 M) glass micropipettes from cells 7 to 9 days after plating. Ethanol produced a temperature-dependent, dose-related depolarization of the myotubes. Maximum depolarization of 15 mV was reached at a concentration of 217 mM at 37°C; at 25°C, ethanol caused hyperpolarization at low concentration (21.7 mM) and was without effect at higher concentrations (up to 435 mM). Of other alcohols examined, only propanol had a significant effect on transmembrane resting potential (Em). In the presence of ouabain, a specific Na-K pump inhibitor, ethanol had no effect on Em. Ethanol decreased the relation between Em and [K⁺]₀. At 37°C, spontaneously occurring action potentials were abolished completely by ethanol, but at 25°C their frequency was reduced. Amplitude, overshoot, rates of rise and fall were all increased by ethanol (21.7 mM). We also found that ouabain-dependent ⁸⁶Rb uptake was decreased by 217 mM ethanol at 37°C and was without effect at 25°C, and that this phenomenon was increased by 21.7 mM ethanol at the lower temperature. We conclude that ethanol effects on Em are exerted primarily via changes in activity and contribution of the Na-K pump to Em.