Age-related Changes of .ALPHA.-Tocopherol Transfer Protein Expression in Rat Liver.

Abstract

Developmental changes in expression of α-tocopherol transfer protein (α-TTP) after birth were investigated using rats with respect to plasma changes of tocopherols. The expression of α-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 four weeks. During the suckling period, the plasma ratio of α-tocopherol to γ-tocopherol linearly increased, because plasma α-tocopherol which was low immediately after birth, increased rapidly during the period, while γ-tocopherol remained unchanged. The increase in the ratio seemed to correlate with the developmental expression of α-TTP in the liver during this period. The ratio also reached the adult level after four weeks. The expression of α-TTP was investigated using primary cultured rat hepatocytes. The expression of α-TTP was found to be extremely low after 20h of culture. The decrease in a-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 α-TTP may be affected by the state of hepatic differentiation.