Female rats were fed vitamin E deficient, control 50 ppm vitamin E, and high vitamin E 300 ppm diets containing 7% corn oil and 3% cod liver oil, and were administered gradually increasing levels of nitrate (up to 1600 ppm), then nitrite (up to 3000 ppm), in their drinking water over a 25-week period. A decreased growth rate was observed in the nitrate/nitrite-treated rats when vitamin E levels were low or zero, but not when a high level of vitamin E was present. Blood methemoglobin levels were monitored over the 25-week period and were found to be unaffected by the level of dietary vitamin E. This study suggests that red blood cell membrane stability does not affect methemoglobin formation. Temporary elevation of methemoglobin levels in the blood was observed with high levels of nitrite administration, however, an eventual reconversion to hemoglobin was achieved even though the high level of nitrite administration was continued. These results suggest that the rats have an inducible, adaptive mechanism to counteract the effects of nitrite ingestion, to a level as high as 3000 ppm in their drinking water.
Bibliographical noteFunding Information:
This project was in part supported by the Univ. of Minnesota Agricultural Experiment Station (Paper No. 10 303) and the University of Illinois Agricultural Experiment Station.