Abstract: The expression patterns and regulations of LDH isozymic system are investigated in the early developmental stages from unfertilized eggs to the one chamber air bladder stage(0-145h) in different combinations between nucleus and cytoplasm of M. anguillicaudatus and P. debryanus. Isozymes are resolved by polyacrylamide gel electrophoresis and then detected by using specific histochemical staining. The expression patterns and regulations of LDH isozymic systems are different in the different combinations of nucleus and cytoplasm. Group I and II had the same cytoplasm of M. anguillicandatus, and the male nucleus genes of LDH are expressed in hybridization group(II)from 3min of post-fertilization to mid gastrula stage. However their gene Products in inbreeding group(I)are not expressed. Some of the isozymic genes in hybridization group are expressed earlier than in inbreeding group. The house keeping enzymes of group I and II are from cytoplasm. Group III and IV have the same cytoplasm of P. dabryanus, the LDH isozmic genes are expressed and regulated by cytoplasm, their house keeping enzymes are very different from those of M. anguillicaudatus. The temporal and spatial expressions and regulations of LDH genes in different combinations between nucleus and cytoplasm are discussed.