NO COEXPRESSION OF LDH-C IN AMAZON CICHLIDS

As commonly found among other advanced teleosts, lactate dehydrogenase (LDH, EC. 1.1.1.27) from cichlid fish exhibits the eye specific LDH-C -4 isozyme. In the last few years, some authors have described the co expression of a distinct liver-specific form in addition to the eye-sp ecific LDH isozymes in cichlid fish. Because liver-specific isozymes h ave been described before in Gadiformes as the product of the same LDH -C locus, such co-expression of these isozymes was explained as the r esult of a fourth locus for LDH. Our studies on Amazon cichlid fishes revealed that the specific isozyme present in liver is the result of a ctivity of another enzyme: alcohol dehydrogenase (ADH, EC. 1.1.1.1.). Several tests with ADH specific staining and the use of ADH inhibitors confirmed that the isozyme described as LDH in liver of Acaronia nass a is actually the result of ADH activity. It is common during the stai ning procedure for LDH and other dehydrogenases such as malate dehydro genase (EC. 1.1.1.37) for the ADH isozyme to also appear. Considering these results, we suggest that LDH occurs as the product of three loci (LDH-A, LDH-B* and LDH-C*) in these fish. (C) 1997 Elsevier Science Inc.