Differential relationship of vitamin A and E levels in methylnitrosourea-induced Sprague-Dawley rats following prolonged feeding of fatty diets enriched with the vitamins.

Prolonged supplementation of vitamins A and E (2500 IU and 11.3 IU/rat daily) in 10.3% and 21.6% fatty diets administered to methylnitrosourea-induced Sprague-Dawley rats caused alterations in plasma and liver levels of both vitamins as well as of the total lipids. Liver vitamin A levels increased steadily (more than fourfold) until termination of the experiment, whereas plasma vitamin A levels only showed a minor increase at the end of the study in comparison to rats fed a standard diet. Liver vitamin E levels initially showed no difference from those of rats treated with a standard diet, and were decreased at the end of the experiment, whereas the respective plasma levels were increased throughout the study, only showing a decrease relative to initial values at termination of the experiment. Plasma total lipids increased with age and following supplementation of the vitamins in the high-fat diet, whereas liver total lipids were influenced less by aging than by the fat and vitamin contents of the respective diets. The observed alterations were, however, not related to significant chemopreventive activity of the vitamins A and E contained in high-fat diets.