Studies on the Deviation of Lactate Dehydrogenase Isozymes in Hepatoma

The nature of lactate dehydrogenase (LDH), (L-lactate: NAD oxidoreductase, EC, 1,1,1,27) has been found to consist of two parent types and three hybrid forms. The two parent types are H4 and M4, and the hybrids may be referred to as H3M, H2M2, and HM3 which corresponds to the random association of subunits in tetramer. Using pig LDH preparations, in vitro molecular hybridization was performed. Quantitation of the resulting isozyme distributions and a comparison with that expected from the binomial distribution demonstrated that random association of subunits occurred as proposed by Markert. Based on this concept, the LDH isozyme patterns and LDH pI isozyme patterns of normal adult livers, fetal livers and hepatoma tissues were studied. The isozyme patterns in hepatoma were of an intermediate type between normal adults and fetal livers. The LDH subunit compositions of normal human livers were similar to a 1:9 mixture of pig LDH-H4 and LDH-M4, however, those of hepatoma tissues were similar to the mixture with a broad range of 1:2?1:5. The results observed above suggest that the LDH isozyme patterns of hepatoma tissues show “fetalism”, which is based on the proportional increase of H subunit. It appears that the wide fluctuation of LDH isozyme patterns observed in the hepatoma tissues are due to the varieties of relative amounts of the LDH-H and LDH-M subunits