Differential effects of fat deficiency on hepatic and pulmonary drug metabolizing enzymes in rat and mouse.

In the present study, we have evaluated the effect of dietary fat deprivation on the carcinogen/drug metabolizing enzymes in rats and mice. In rats, hepatic AHH, Cyt.P-450 Cyt.b5 and Cyt.c-reductase were significantly decreased due to fat deficiency, whereas in lungs, AHH and Cyt.c-reductase were decreased without any change in Cyt.P-450 level. In mice, feeding of fat-free diet did not cause any alteration in hepatic AHH and Cyt.P-450, but the levels of Cyt.b5 and Cyt.c-reductase were significantly reduced. In contrast to liver, Cyt.P-450 and Cyt.b5 were increased in lungs. Activity of UDPGT was lowered both in liver and lungs of rats whereas GST and GSH were increased in liver only. In mice, a decrease in UDPGT and appreciable increases in GST and GSH in liver were observed. However, in lungs, UDPGT activity was enhanced by feeding fat-free diet. These observations suggest that mice and rats respond differentially to the depletion of fat in the diet.