Effect of Aflatoxin on the Biosynthesis and Degradation of Vitamin A

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  • ビタミンＡ生成および分解に及ぼすアフラトキシンの影響
  • ビタミン A セイセイ オヨビ ブンカイ ニ オヨボス アフラトキシン ノ エ

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Aflatoxin is a toxic substance which is contained in Aspergillus flavus grown in rice or peanuts on the tropics. It causes great damage on liver and other organs, especially causes carcinoma in animal liver.<br>In the tropics, we often find vitamin A deficiency. As for one of these reasons, we supposed that aflatoxin must inhibit the converting enzyme activity from β-carotene to vitamin A. To confirm this supposition, we employed a vitamin A deficient rat and examined the effect of aflatoxin on the conversion of β-carotene to vitamin A.<br>Male Sprague-Dawley rats, weighing about 40g, were fed a vitamin A deficient diet for 51 days. Then, they were divided into four groups; the control group, aflatoxin administrated group, aflatoxin and β-carotene administrated group, β-carotene administrated group. After 10 days, they were sacrificed and the contents of vitamin A in the livers were assayed. The body weights of β-carotene group were increasing gradually, but that of the other three groups were decreasing continuously. Contents of vitamin A in liver were highest in the β-carotene group, but were extremely low in the other three groups.<br>The effect of aflatoxin on the degradation of vitamin A was also examined. Amounts of 0.5ppm or 0.2ppm of aflatoxin was administered in rats for 30 days. Rats were killed and their livers were homogenized and centrifuged. The microsomal fraction was used as enzyme solution. The activity of NADPH-cytochrome C reductase and the amount of P-450 were increased by the administration of aflatoxin. From these results, it is concluded that the prolong intake of aflatoxin has a tendency to promote vitamin A degradation.

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