Aldehyde dehydrogenase as a marker for chemically initiated mouse liver tumors

The induction of an aldehyde dehydrogenase isozyme (B-ALDH), which uses aromatic aldehydes such as benzaldehyde as substrate and NADP as a cofactor was examined in normal liver and tumors of B6C3F1 male mice. The tumors were induced by either 15 or 45 ppm diethylnitrosamine (DENA) in the drinking water for 4 weeks. In some cases, the DENA treatment was followed with 500 ppm phenobarbital (PB) in the drinking water. DENA increased the percent of the mice that showed B-ALDH activity in their livers 14 weeks after termination of DENA treatment. The B-ALDH activity was confined mainly in the centrilobular region. Fifty weeks after the termination of the DENA treatment the percent of animals with B-ALDH in their livers was not different from control mice. However, a larger number of the tumors exhibited B-ALDH activity. These studies show that B-ALDH is a good histochemical marker for mouse liver tumors and may be useful as a marker for the effect of chemical carcinogens in this species.