Lactate dehydrogenase isoenzymes in mucosal biopsy specimens from patients with ulcerative colitis.

Biopsy specimens from long-standing ulcerative colitis were frozen shortly after resection and homogenized before measurement of lactate dehydrogenase (LD) isoenzymes by agar electrophoresis. Results were related to histological changes in inflammation or dysplasia. The percentage of total LD M monomers was significantly higher in homogenates of specimens with dysplastic changes than in homogenates of specimens with only inflammatory changes. A positive correlation was found between total LD M monomers and LD5 monomers (isoenzyme) for the whole material, for each of the histological subgroups of ulcerative colitis, and for the control specimens of adenomas, carcinomas, and normal mucosa. A positive correlation between total LD activity and total percentage of LD5 monomers was only seen for dysplastic, adenomatous, and malignant tissues. The results support the use of dysplasia as a marker for premalignant changes in mucosal specimens and indicate a possible role for LD isoenzyme measurements in specimens from patients with long-standing ulcerative colitis.