Retention of Pacemaker Activity in Mammalian Myocardial Cells recovered from Liquid Nitrogen

Abstract

SUCCESSFUL preservation of the mammalian heart in the frozen state is not yet possible because of the sheer bulk of the organ as well as difficulties at the cellular level¹. Pacemaker activity must be retained, however, and so I have made preliminary studies of sustained rhythmic contractions in dissociated cells. A pacemaker cell in culture is one which, although isolated from contact with neighbours, beats rhythmically². A method for freeze-preservation of sheets of beating rat myocardial cells and myocardial cells frozen in suspension has been described³, using dimethyl sulphoxide as a cryoprotective agent, in which resumption of contractility was observed on thawing. Estimates of restoration, however, were made on dense populations of cells in confluent sheets, which would be expected to produce a high proportion of beating cells, as myocardial cells capable of pacemaker activity can drive responsive neighbours with which they may come in contact⁴.