STUDIES ON MECHANISM OF FREEZING DAMAGE TO MOUSE LIVER USING A MITOCHONDRIAL ENZYME ASSAY .2. COMPARISON OF SLOW AND RAPID COOLING RATES

By comparison with a variety of other electron transport components, the succinate cytochrome c reductase complex was found to be particularly senstive to, and suitable for evaluating, freeze-thaw damage. The use of a variety of freezing procedures demonstrated loss of half the activity of this enzyme complex, with little variation, over a large range of freezing rates, from 1°C per min to those produced by quenching in liquid nitrogen and isopentane. Quenching in liquid propane, however, produced a marked additional increment of damage resulting in a total loss in enzyme activity of 80%. The basis for the excess damage produced by liquid propane is believed to be related to its cooling rate, rather than to any peculiar solvent action, because maximal damage is produced within a few seconds and is not increased upon prolonged standing in the medium, and because the excess damage can be prevented by prefreezing the tissue in other media. © 1969.