Cryoprotectant-treated myocardium evaluation

Whole excis ed rat hearts were treated with 5, 10, or 15% (v/v) dimethyl sulfoxide/glycerol and then some were frozen in liquid nitrogen while the balance remained unfrozen. Freezing and thawing rates were approximately 30degreesC/min. Ventricular tissue was examined for histological damage, glycogen depletion, and enzyme sites, using histological, histochemical, and electron microscopy techniques. Early signs of cellular degeneration and ischemia were observed in all unfrozen groups; depletion of glycogen reserves, fuchsinophilic staining, vacuolization and granulation of the sarcoplasm were noted. Results from frozen groups were similar, but ultrastructural damage was more severe and extensive. Alkaline phosphatase and succinic dehydrogenase sites were abundant in unfrozen specimens and absent or markedly reduced in frozen specimens which also exhibited widespread nonspecific staining throughout intercellular spaces.