Frozen fetal and neonatal mouse cardiac reimplants for assessing cryoprotective agents

The electrical activity of transplanted syngeneic 17–19 day fetal and 1–9 day neonatal mouse hearts has been studied after freezing to −196 °C in the presence of different cryoprotective agents. Histological examinations were performed after electrical activity (QRS) had been studied for periods in excess of 30 days. EG, DMSO, and glycerol appear equally protective provided that glycerol is added at 37 °C. Methanol, although nontoxic at those concentrations which will protect tissue culture cells, does not offer protection to this type of organized tissue. None of the high molecular weight compounds tested offered cryoprotection in this system. Diffusion of both protective agents and nutrients has been shown to be limiting factors in the survival of frozen-thawed neonatal hearts between 6 and 9 days of age.