Absorption and tissue distribution of all-trans and 9-cis β-carotene in the preruminant calf

These studies utilize the preruminant calf animal model to compare the absorption of all-trans -carotene (ßC) to 9-cis BC and of all-trans BC to cholesterol and triglycérides (TG). In the first study, 2 male Holstein calves were fed twice daily for 7 days with either 10 mg of all-trans ßC as 10% water-soluble beadiets (Hoffmann-La Roche) or 10 mg total all-trans + 9cis BC as Betatene(tm) water-dispersible powder (1.5 ratio all-trans:9-cis BC). On the eighth day, calves were killed 2 h following a BC enriched meal. Tissue samples were analyzed by HPLC for the all-rrans:9-cis BC ratio. Alltrans BC was the predominant (>95%) isomer in all tissues of the calf fed all-trans BC. In the calf fed the Betatene(tm) powder, the all-trans:9-cis BC ratio was highest in the serum, adipose tissue, adrenal gland and intestinal mucosa (41.7, 40.6, 59.2 and 86.1, respectively). Tissues with the lowest ratios were the liver, spleen and lung (1.5,13.1 and 18.7, respectively). This suggests that the circulation and tissue distribution of 9-cis BC may be more highly regulated than that of the all-trans isomer. In the second study, 1 male Holstein calf was fed 20 mg all-trans BC as water-soluble beadiets along with 30 (iCi of 14C labeled cholesterol as part of a morning meal followed by a second carotenoid-free meal at 8 h. Chylomicrons (CM) were analyzed for ßC, TG and 14C radioactivity. CM BC and 14C both peaked at 5 h post-dosing with a second peak occurring at 10 h. CM TG peaked at 2 h post-dosing with a second peak occurring at 10 h. This study suggests that the absorption mechanism for all-trans BC is similar to cholesterol and that both are delayed as compared to the absorption of TG.