Effect of Dilution on the Lactic Dehydrogenase Isozyme Pattern obtained in the Starch Gel

Abstract

THE demonstration of the heterogeneity of lactic dehydrogenase (LDH) activity in human serum and red cells¹ was followed shortly by a report describing LDH heterogeneity in tissues of other mammals². Multiple molecular forms of LDH have been utilized in clinical medicine^1,3–5, embryology⁶ and tissue culture⁷. Markert and Møller directed attention to the general phenomenon of multiple enzymatic forms exhibiting similar substrate specificities within a cell by designating them isozymes⁶. Recent reports have indicated that tissue homogenization⁸ and enzyme purification⁹ may alter the pattern of isozymes observed in the starch gel. The present communication shows that the LDH isozyme pattern obtained may be altered by changing the concentration of enzyme activity applied to a starch gel prior to electrophoretic separation. The distribution of total LDH activity among the 5 LDH isozymes of human leucocytes and muscular tissue varies according to the amount of activity applied (Fig. 1). Since relative activities of the serum LDH isozymes have been used in the diagnosis of disease states^1,3–5, it is important to specify the total amount of activity applied prior to electrophoresis.