Argon laser microirradiation of mitochondria in rat myocardial cells in tissue culture. V. Pacemaker versus non-pacemaker cells

Abstract

Abstract Rat myocardial cells in vitro were irradiated with a laser microbeam in order to more fully define the nature of beating (“pacemaker”) and non-beating (“non-pacemaker”) cells. Cells were observed for several hours prior to their association into two-cell groups. Irradiation was performed on those two-cell groups where one of the two cells was a non-beater prior to association with a contracting cell. In 80% of the cases where the cell that was killed was the non-beater, the remaining cell (the beater) continued to contract normally. In 40% of the cases where the killed cell was the “beater” the non-beater continued to contract. These results suggest that cells classified as non-beaters prior to association with a beater, are capable of contracting on their own after the association with a beating cell is eliminated. It is concluded that the non-beating state is not immutable.