Cultivation, morphology, and electrophysiology of contractile rat myoballs.
Myoballs were cultured from neonatal rat skeletal muscle without the use of antimitotic drugs. Electron microscopic investigation showed that 7-day-old myoballs are multinucleated syncytia in a state of differentiation where filaments are abundant and already in hexagonal arrays. The resting potential of 142 myoballs kept at 20 degrees C was not correlated with the cell size. Its mean value was -64 mV. Cells with a high resting potential were capable of generating action potentials with a threshold of -51 mV, an overshoot of +31 mV, and a rate of rise of 100 V/s. The steady-state current-voltage relation showed inward rectification on hyperpolarization and outward rectification on depolarization. The dynamic sodium and potassium currents were investigated at 37 degrees C with the whole-cell-recording technique. The sodium current had its maximum at -20 mV. The potassium current showed delayed activation and a very slow and incomplete inactivation. The electrophysiological results from these cultured cells are very similar to those obtained from adult cells.
D000200:Action Potentials; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003402:Creatine Kinase / Q000378:metabolism; D004558:Electric Stimulation; D008564:Membrane Potentials; D008854:Microscopy, Electron; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains
D003402:Creatine Kinase