Release of intracellular enzymes into serum

Abstract

Serum lactic acid dehydrogenase (LDH) activity of normal rabbits is increased after intramuscular injections of peanut oil suspensions of dialyzable saline extracts of heart, kidney, liver, or lung tissue from normal rabbits, and after injections of histamine. Activity is maximal by 24 h and normal by 48 h after injection. The LDH isoenzyme patterns of the sera obtained after the administration of the tissue extracts differ markedly from each other and from the LDH isoenzyme patterns of the tissues extracted. They also differ from the serum LDH isoenzyme patterns obtained after the administration of histamine. These results suggest that histamine is not the active substance present in the tissue extracts, that the active materials in the tissue extracts are different from each other, and that the tissue extracts probably do not effect the release of LDH from the kind of tissue used in their preparation. The active substances in the tissue extracts differ in their heat stabilities, are stable when lyophilized, and are adsorbed by Dowex 1 (Cl−) but not by Dowex 50 (H+). These findings suggest that cells contain low molecular weight substances which have the potential of releasing LDH, and presumably other proteins also, from the cells of other tissues.