Lactate dehydrogenase isoenzyme 1 (LDH-1) in athymic mice with xenografts of a human testicular germ cell tumor.

Lactate dehydrogenase (LDH) and LDH isoenzyme activities were determined in tumor tissue, tumor cystic fluid, and serum from athymic mice with transplants of a human testicular germ cell tumor. High activity of LDH-1 was found in tumor tissue and tumor cystic fluid. By histochemical staining LDH was found in all tumor cells. Most tumor cells had a faint staining reaction while some cells dispersed throughout the tumor had a strong staining reaction. The serum LDH-1 in athymic mice with tumor transplants correlated markedly with the tumor volume. The results indicate that serum LDH-1 was derived from the testicular germ cell tumor transplants.