Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on vitamin A metabolism in mice |
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Authors: | Yang Yan-Mei Huang Dong-Yang Liu Ge-Fei Zhong Jiu-Chang Du Kun Li Yi-Fan Song Xu-Hong |
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Institution: | Molecular Biology Center, Medical College of Shantou University, 22 Xin Ling Road, Shantou 515041, People's Republic of China. |
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Abstract: | This study aimed to clarify the effects of single and repeated administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the activities or expression of some metabolic enzymes of retinoids and the influence of supplemental vitamin A on changed vitamin A homeostasis by TCDD. In Experiment I, the mice were given a single oral dose of 40 mug TCDD/kg body weight, with or without continuous administration of 2,500 IU vitamin A/kg body weight/day, and were killed on day 1, 3, 7, 14, and 28. In Experiment II, the mice were daily given 0.1 microg TCDD/kg body weight, with or without supplemental 2,000 IU vitamin A/kg body weight, and were killed on day 14, 28, and 42. In both experiments, TCDD significantly decreased the hepatic all-trans-retinol level and increased the hepatic all-trans-retinoic acid (RA) content, increased the mRNA and enzymatic activities of retinal oxidase. In TCDD + vitamin A mice, the all-trans retinol content was significantly higher, and the retinal oxidase mRNA was significantly lower on day 3 or 7 in Experiment I and on day 14 in Experiment II, compared to TCDD-treated mice. The induction of the retinal oxidase may contribute to the decrease in hepatic all-trans-retinol level and the increase in hepatic all-trans-RA caused by TCDD. Supplemental vitamin A might decelerate the effect of TCDD on retinal oxidase mRNA. |
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Keywords: | 2 3 7 8‐Tetrachlorodibenzo‐p‐dioxin Vitamin A Retinal Oxidase Lecithin:Retinol Acyltransferase Retinoic acid |
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