Exposure to the carcinogen benzopyrene depletes tissue vitamin A: beta-carotene prevents depletion.
Evidence in humans and laboratory animals supports a cancer-protective effect of vitamin A, but the mechanism remains unclear. While vitamin A deficiency causes squamous metaplasia, and lung cancer patients have lower vitamin A status, their serum vitamin A levels are not indicative of deficiency. We hypothesize that local enzymatic degradation of vitamin A can be induced by exposure to carcinogens such as benzopyrene found in cigarette smoke. This study was designed to determine if benzopyrene exposure depletes tissue vitamin A and whether beta-carotene might prevent the depletion. Weanling male Fischer rats were fed a nutritionally complete purified diet, supplemented with or without benzopyrene at 400 mg/kg feed or beta-carotene at 2 g/kg feed. Vitamin A content of the liver, small intestine, and serum was determined by high-performance liquid chromatography. There was no effect of benzopyrene feeding on serum retinol levels through four weeks. However, there was a decline in tissue retinol in the liver and small intestine by two weeks, with a 30% decline by four weeks (p less than 0.05). In rats fed beta-carotene, there was no effect of benzopyrene on tissue vitamin A level. These results indicate that exposure to benzopyrene induces a local tissue vitamin A depletion despite a vitamin A-sufficient diet and maintenance of serum vitamin A levels. A high intake of beta-carotene prevented the vitamin A depletion effect of benzopyrene exposure. Further studies appear warranted to determine whether some of the adverse effects of environmental carcinogens, as found in cigarette smoke, charcoal-broiled meats, and industrial wastes, might be alleviated by dietary intervention.
Edes
T E
TE
Department of Medicine, Harry S. Truman Memorial Veterans Hospital, Columbia, MO.
Gysbers
D G
DG
Buckley
C S
CS
Thornton
W H
WH
D000704:Analysis of Variance; D000818:Animals; D001580:Benzopyrenes / Q000009:adverse effects*; D002338:Carotenoids / Q000494:pharmacology*; D007421:Intestine, Small / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D014018:Tissue Distribution; D014801:Vitamin A / Q000378:metabolism*; D019207:beta Carotene
D001580:Benzopyrenes; D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids