Intestinal absorption of alpha-tocopherol in the unanesthetized rat. The influence of luminal constituents on the absorptive process.

3H-alpha-tocopherol intestinal absorption was studied in the unanesthetized rat. The rate of alpha-tocopherol absorption remained linear over a wide range of concentrations (4 nM to 400 micrometer). Increasing the sodium taurocholate concentration in the micellar infusate up to 15 mM did not increase the rate of absorption of the vitamin. Addition of long-chain fatty acids to the micellar infusate decreased the absorption rate of the vitamin (p less than 0.05). The decrease was most significant (p less than 0.01) following the addition of the polyunsaturated linolenic (C18:3) acid. Increasing the hydrogen ion concentration in the perfusate increased the absorption rate of alpha-tocopherol. The present experiments in vivo support the conclusions drawn from in vitro uptake experiments which indicated that alpha-tocopherol is absorbed by a passive diffusion process. These experiments indicate that micellar expansion with polyunsaturated fatty acids interferes with the absorption of alpha-tocopherol and may result in deficiency of the vitamin.