EFFECT OF RED PALM OIL ON SOME HEPATIC DRUG-METABOLIZING-ENZYMES IN RATS

Red palm oil (RPO) from Elaeis guineensis is being considered for use as an edible oil in India as it is one of the richest natural sources of carotenoids. The effect of RPO on the host detoxification system, w hich is a vital mechanism in cancer prevention, was studied in three s eparate batches of Wistar/NIN inbred albino rats, and compared with co ntrols, groundnut oil (GNO) and refined bleached deodorized palmolein oil (RBDPO). The first batch of 36 rats (12 from each group) comprised the adult males (26 wk old) of the third generation (F2b) from a mult igeneration reproduction study in which three groups were fed 10% GNO or RPO or RBDPO for three generations continuously. Phase II glutathio ne-S-transferase (GSH-T) activity was measured in the liver cytosol of these rats after they had twice completed the process of mating, gest ation, lactation and weaning, because GSH-T is one of the principal de toxifying enzymes involved in conjugating reactions of phase II metabo lism. The fourth generation (F3b) weanling rats of the three groups, r eceiving GNO, RPO or RBDPO, were continued on the 10% oil diet for 9 w k, after which cytosolic GSH-T activity was measured. In the second ex periment, eight male weanling Wistar/NIN inbred albino rats, 5 wk old, weighing 100-120 g, were fed 10% GNO, RPO or RBDPO for 4 wk in a 20% protein synthetic diet. Liver cytosolic GSH-T, reduced glutathione, mi crosomal total cytochrome P-450, aminopyrine N-demethylase and ethoxyr esorufin-O-deethylase activity were measured to elucidate the effect o f RPO on some phase I and phase II reactions. Significantly higher lev els of GSH-T were observed in F2b and F3b rats given RPO than in those given GNO or RBDPO. In the second experiment, GSH-T induction was als o noted, together with increased levels of reduced GSH. Phase I enzyme s and total cytochrome P-450 levels were comparable between groups, in dicating that no induction attributable to RPO had occurred. Thus, enh ancement of one of the detoxifying phase II enzymes, in conjunction wi th the lack of induction of those activating phase I enzymes that are known to metabolize phenobarbitone and polycyclic aromatic hydrocarbon s, suggests that RPO affords protection against chemical carcinogens, probably because of its carotenoid content.