Developmental changes in alpha-tocopherol, especially during infantile period.

Abstract

Developmental changes in expression of alpha-TTP after birth were investigated using rats with respect to plasma changes of tocopherols. The expression of alpha-TTP in the neonatal rat liver, which was very low immediately after birth, increased steadily during the two weeks of life before weanling and reached the adult level at 4 weeks. During the suckling period, the plasma ratio of alpha-tocopherol to gamma-tocopherol linearly increased, because plasma alpha-tocopherol was low immediately after birth, increased rapidly during the period, while gamma-tocopherol remained unchanged. The increase in the ratio seemed to correlate with the developmental expression of alpha-TTP in the liver during this period. The ratio also reached the adult level after 4 weeks. The expression of alpha-TTP was investigated using primary cultured rat hepatocytes. The expression of alpha-TTP was found to be extremely low after 20 h of culture. The decrease in alpha-TTP expression was exacerbated by adding epidermal growth factor to the culture medium and was inhibited by adding dexamethasone. These observations suggest that expression of alpha-TTP may be affected by the state of hepatic differentiation. The Western and Northern blot analysis of alpha-TTP in vitamin E deficient and enriched rats were compared to control rats. The decrease of mRNA of alpha-TTP observed in alpha-Toc-enriched rat liver and the increase of mRNA observed in the vitamin E deficient rat liver indicate the synthesis of alpha-TTP, although alpha-TTP itself was not altered.