AJP - Cell Physiology, Vol 245, Issue 5 381-C387, Copyright © 1983 by American Physiological Society
Tetrodotoxin-sensitive Na+ channels in isolated single cultured rat myocardial cells
N. Matsuki and K. Hermsmeyer
We studied the existence of tetrodotoxin (TTX)-sensitive fast Na+ channels
in isolated single (verified by dye injection) myocardial cells compared
with small multiple-cell groups from 1- to 3-day-old rat ventricles in cell
culture. For single cells, average values were -63 mV maximum membrane
potential, 32 mV overshoot, and 65 V/s maximum rate of rise of the action
potentials (+Vmax). These values were comparable to values from groups of
multiple (2-10) cells. TTX strongly depressed +Vmax dose dependently, with
no difference between single and multiple cells. +Vmax was also decreased
by lowering extracellular Na+ concentration but not by D 600 or lowering
extracellular Ca2+ concentration. These results suggest that 1) isolated
single cells possess TTX-sensitive fast Na+ channels, 2) culturing per se
does not alter TTX sensitivity, and 3) TTX sensitivity is not modified by
cell density.
