Improved column method for separating lactate dehydrogenase isoenzymes 1

Lactate dehydrogenase (ID) isoenzymes 1 and 2 in human serum were separated on a column of diethyiaminoethyl-Sephadex. Samples layered on mini-columns were eluted with buffered sodium chloride (100, 150, and 200 mmoi/ liter). Lactate dehydrogenase activity in column effluents was mea&red by the Wacker method, and their isoenzyme content was evaluated by electrophoresis on polyacryl-amide gel. Results for column-fractionated LD-1 and LD-2 were expressed in two ways: LD- 1/LD-2 ratios and total LD-1 + LD-2 activities. The former is a more specific in-dicator of myocardial infarction than the latter. Sera from 10 patients with acute myocardial infarction (increased creatine kinease isoenzyme MB activity) exhibited ratios in the range of 0.92 to 1.56, ratios for 10 patients without heart disease (normal creatine kinase MB) ranged from 0.33 to 0.69. Previously, I described a column procedure for the simul-taneous separation of creatine kinase (CK) isoenzyme MB and lactate dehydrogenase (LD) isoenzymes 1 and 2 (1).1 CK isoenzyme was measured free from isoenzymes MM and BB, but LD isoenzymes 1 and 2, although free from LD-3, 4, and 5, were measured in combination (LD-1 + LD-2). Here, I de-scribe a column procedure specifically designed to separat