Increase of low-Km NADPH-dependent aldehyde reductase activity in the brain by chronic treatment of rats with barbital.

Kinetics studies showed two apparent Km values for p-nitrobenzaldehyde. The high-Km aldehyde reductase (ALR) had a lower Ki value for barbital than the low-Km ALR. The value for maximal velocity (Vmax) for the high-Km ALR was not changed by chronic barbital treatment. However, the Vmax value for the low-Km ALR was significantly increased by chronic barbital treatment. These results suggest that during barbital treatment low-Km ALR which is less sensitive to barbital is induced in compensation for the decreased aldehyde metabolizing capacity of brain.