VITAMIN-E ENHANCES THE LYMPHATIC TRANSPORT OF BETA-CAROTENE AND ITS CONVERSION TO VITAMIN-A IN THE FERRET

Backgound/Aims: beta-carotene and alpha-tocopherol may have either antagonistic or synergistic effects on each other's absorption and metabolism. The effects of both physiological and pharmacological concentrations of alpha-tocopherol on the absorption and metabolism of beta-carotene in ferret intestine were determined. Methods: A high concentration of beta-carotene was perfused through the upper portion of the small intestine of ferrets in vivo with varying levels of alpha-tocopherol. The effluent of a mesenteric lymph duct cannulation, the intestinal mucosa scraping, and portal vein blood were sampled and analyzed by high-performance liquid chromatography. Results: The lymphatic transport of beta-carotene was enhanced 4-fold by alpha-tocopherol at a physiological dose and 12-21-fold at a pharmacological dose. The lymphatic transport of alpha-tocopherol was linearly (r = 0.8; P < 0.05) related to the luminal alpha-tocopherol concentration even in the presence of a high concentration of beta-carotene. Furthermore, alpha-tocopherol increased the conversion of beta-carotene into retinol in the intestine in a dose-dependent manner. Conclusions: alpha-Tocopherol has a positive effect on the intestinal absorption of intact beta-carotene and may modulate the metabolic conversion of beta-carotene into retinoids.