Ultrastructure-function correlative studies for cardiac cryopreservation. II. Hearts frozen to various temperatures without a cryoprotectant

Isolated rat hearts were perfused with balanced salt solution (BSS) for 20 min, sealed in a metal cannister, and cooled in a ?20 °C acetone bath at a rate of 1 °C/min to one of four subzero core temperatures (?10, ?12, ?17, or ?20 °C). Upon attainment of the desired temperature the hearts were rapidly thawed (40–50 ° C/min) and reperfused with BSS for an additional 20 min. Approximately half of the hearts cooled to ?10 or ?12 °C resumed spontaneous contractile activity after thawing. One of 16 hearts survived cooling to ?17 °C, while no heart survived cooling to ?20 °C. Nonfrozen controls gave a positive inotropic response to a standard test dose of ouabain; none of the thawed survivors did.