抄録
The present experiment was conducted to study the effects of dietary vitamin E on plasma corticosterone (CTC) concentration and adrenal steroid syntheses in chickens treated with adrenocorticotropic hormone (ACTH). Chickens were divided into ACTH (-) and ACTH (+) groups, and each group was further divided into three subgroups adminis-tered with vitamin E (500 or 5, 000 mg/kg diet) and without the vitamin. Vitamin E (DL-α-tocopheryl acetate) was mixed with the basal diet at levels of 500 and 5, 000 mg/kg and fed for 6 d. ACTH (20 IU/kg body weight) was given daily by intraperitoneal injection for 5 d. α-Tocopherol levels in the plasma and adrenal gland were markedly elevated by vitamin E feeding, and the level of adrenal free cholesterol (CHOL), which is used for steroid synthesis, was significantly decreased by vitamin E feeding in a dose-dependent manner. However, the level of adrenal CHOL ester was unchanged by any treatment. The elevations of preg-nenolone, progesterone and CTC levels in the adrenal gland of chickens with ACTH treat-ment were decreased by vitamin E administration. The elevation of plasma CTC concentra-tion in the ACTH (+) group was dramatically decreased by vitamin E administration, while that concentration was not influenced by the vitamin administration in the ACTH (-) group. These findings indicate that vitamin E suppresses the elevation of the plasma CTC concentration due to ACTH in chickens, possibly by inhibiting the conversion of CHOL ester to free CHOL in the adrenal gland.
