Lymphatic and portal absorption of vitamin E in aging rats.

We studied the intestinal absorption and lymphatic versus portal distribution of vitamin E and its metabolites in vivo in young (4 month), "middle-aged" (14 month), and old (24 month) male Sprague-Dawley rats. Twenty-four hours after its surgical preparation, the rat's jejunum was infused with a physiological micellar solution containing 200 nM alpha-tocopherol. Its transport rate into lymph and bile as well as its accumulation in liver and intestinal tissues was measured. Lymphatic transport of vitamin E increased from 92 to 269 pmol/5 hr and bile appearance of vitamin E and its polar metabolites increased from 230 to 298 pmol/5 hr as rats aged. Tissue accumulation of the vitamin in the small intestine and liver increased significantly with aging (P less than 0.05). Total absorption of the vitamin and its intestinal metabolites increased from 5912 pmol/5 hr in young rats to 16,467 pmol/5 hr in old rats (P less than 0.01). Absorption expressed as a percentage of infused alpha-tocopherol increased from 19.7% at 4 months to 54.9% at 24 months. These studies demonstrate an aging-associated increase in the total amount of vitamin E absorbed and a shift from portal to lymphatic transport. These changes may represent a salutary adaptive increase in the systemic availability of vitamin E with aging.