An Analysis of the Isoenzymes of Creatine Phosphokinase and Lactic Dehydrogenase in the Esophagus

Surgical manipulation of muscular organs can cause alterations of the serum isoenzymes of creatine phosphokinase (CPK) and lactic dehydrogenase (LDH), which are frequently used to confirm the diagnosis of myocardial infarction (MI). Since the content of these enzymes and their isoenzymes has not been established for the esophagus, an experiment was conducted to evaluate and compare the enzymes in postmortem specimens from humans and fresh canine specimens. One gram transmural esophageal sections were taken from specimens having no demonstrable disease. All samples were homogenized individually in Ringer's lactate solution and centrifuged, and the supernatants were analyzed for the respective isoenzyme distributions by agarose gel electrophoresis. From the study we drew the following conclusions: (1) all three isoenzymes of CPK (including CPK-MB, the myocardial isoenzyme) are present in the esophagus; (2) LDH₁, the isoenzyme of LDH most prevalent in myocardium, is the least common of the five isoenzymes of LDH in the esophagus; (3) the dog is an appropriate model for studying changes of these isoenzymes after operation; and (4) any potential confusion in diagnosing postoperative MI due to esophageal CPK-MB in the serum can be resolved, theoretically, by analyzing LDH serum isoenzymes. In myocardial infarction, LDH, becomes the predominant isoenzyme, whereas esophageal injury should be associated, theoretically, with a serum LDH isoenzyme pattern in which LDH₁ is the least prevalent isoenzyme.