Cytochemical changes in lactate dehydrogenase isoenzymes in human brain tumours

The lactate dehydrogenase (LDH) isoenzyme patterns in benign and malignant brain tumours were determined by means of electrophoresis of the cell extracts and selective cytochemical stain of the smears. The LDH isoenzyme distribution of the cell extracts showed a pronounced cathodal shift in the malignant gliomas and metastatic carcinomas. Normal brain tissues and histologically benign gliomas, however, showed an anodal pattern with a dominance of the H-type LDH. Schwannomas and meningiomas had a midzone isoenzyme pattern with a dominant LDH3 fraction. Pituitary adenomas usually showed the LDH pattern similar to that of the normal cerebrum. The LDH M fraction could be cytochemically verified using an inhibitory effect by 2.6 M urea in staining. Astrocytomas grades 3-4 and metastatic carcinomas were characterized by loss or marked reduction of stainability by urea treatment, while astrocytomas grades 1-2 and oligodendrogliomas were resistant to urea inhibition.