Membrane potential oscillations in enzymatically isolated rat myocardial cells.
Enzymatical isolation was used for preparation of single myocardial cells, contractions of which were mainly of slow phasic type but normal fast contractions also occurred. Membrane potential (MP) changes of these cells were measured by conventional microelectrode techniques. Initial MP level of these cells varied between -60 to -90 mV (74.4 +/- 1.9). In the majority of the cells the MP rapidly dropped to -20 to -40 mV and continued to decline while oscillating. In some cells MP recovered from -20 to -40 back to a more negative potential, and the MP oscillation was strongest (up to 20 mV) between -30 to -50 mV. In about 3% of the impalements the MPs did not degenerate at all, but stayed at initial values for several minutes. The MP oscillations were dependent on the MP level and connected to the slow phasic contractions. In connection to the normal fast contractions, two types of action potentials (AP) could be registered. Near -50 mV the cells often generated slow APs of duration 200-400 ms and dV/dt less than 3 V/s but at higher MP level normal fast APs up to 120 mV (100-300 ms and dV/dt greater than 40 V/s) were generated. The slow phasic contractions were never connected to either type of AP.
D000200:Action Potentials; D000818:Animals; D002469:Cell Separation / Q000379:methods; D005071:Evoked Potentials; D008297:Male; D008564:Membrane Potentials; D009200:Myocardial Contraction; D009206:Myocardium / Q000166:cytology*; D009991:Oscillometry; D051381:Rats; D011919:Rats, Inbred Strains