Radiation-induced enzyme efflux from rat heart: sedentary animals.

Serum levels of lactate dehydrogenase, creatine kinase, and glutamate oxaloacetate transaminase show initial elevations within 12 hr of exposure to 2,000 rads of gamma-radiation to the thoracic region of rats. Significant decreases in heart muscle homogenate levels of these enzymes parallel initial elevations in the serum and may suggest that enhanced leakage of enzymes is a consequence of radiation injury to heart muscle. Insignificant alterations in mitochondrial glutamate oxaloacetate transaminase levels after exposure indicate that in vivo injury to the mitochondria from therapeutic levels of gamma-radiation is questionable. The results support the contention that ionizing radiation instigates alterations in the dynamic permeability of membranes, allowing leakage of biologically active material out of the injured cell.