Studies of lactic dehydrogenase content in rectal mucosal biopsies.

The total lactic dehydrogenase (LD) content and LD isoenzyme ratios were studied in homogenized rectal mucosa from 31 patients with established non-specific mucosal ulcerative colitis and from 16 normal subjects. The total LD content was found to be significantly increased in patients with active ulcerative colitis when compared with patients with inactive colitis or with normal subjects. There was a similar though not a significant increase in the slow moving isoenzymes of LD in samples of rectal mucosa from patients with active colitis. The LD isoenzyme pattern was in the normal range in two of the three patients with histological premalignant changes in rectal biopsy specimens. There was a statistically significant linear correlation between the total lactic dehydrogenase content of rectal mucosa and the carcino-embryonic antigen levels in whole serum. Both the total content and isoenzyme ratios of LD were increased in neoplastic tissue obtained from patients with carcinoma of the colon and with tissue from benign rectal polyps.