The accumulation of alpha- and beta-carotene in serum and tissues of preruminant calves fed raw and steamed carrot slurries.

The preruminant calf model was used to evaluate the effects of mild heat treatment on the serum and tissue accumulation of alpha- and beta-carotene from carrots. Twenty-four 1-wk-old Holstein male calves were assigned to one of four groups and fed a milk replacer diet. Negative control animals received no additional supplement. The three remaining groups received an additional 20 mg beta-carotene/d from either water-soluble beadlets, homogenized raw carrots or homogenized steamed carrots. Serum samples were obtained daily, and calves were killed after 7 d and samples of serum, liver and adrenal collected. Tissue and serum alpha- and beta-carotene concentrations were not significantly higher in steamed carrot-fed animals than in raw carrot-fed animals. The molar ratios of beta-carotene to alpha-carotene in both raw carrot-fed and steamed carrot-fed groups were highest in adrenal tissues, intermediate in serum and lowest in the diets. None of these differences were statistically significant. When the serum, liver and adrenal beta-carotene data were pooled, the mean relative accumulation of beta-carotene, expressed as a percentage of the mean response of calves receiving water-soluble beadlets, was 46.8% for calves fed raw carrots and 74.0% for calves fed steamed carrots. These results suggest a small enhancing effect of mild heat treatment of carrots on the serum and tissue accumulation of carotenoids.

Evaluation of the preruminant calf as a model for the study of human carotenoid metabolism.

This study evaluated the preruminant calf as an animal model for the study of human carotenoid metabolism. Fifteen newborn male Holstein calves were fed a carotenoid-free milk replacer diet to maintain them in the preruminant state. After a 7-d adjustment period, three calves were killed and 12 calves received a single oral dose (20 mg) of beta-carotene in the form of water-soluble beadlets. Blood samples were collected periodically and samples of various tissues were collected when the calves were killed. Three animals each were killed by exsanguination at 1, 3, 6 and 11 d post-dosing. Serum beta-carotene concentrations peaked between 12 and 30 h post-dosing and declined slowly afterwards. Serum data were fitted to a two-compartment model and yielded an elimination constant (k2) that was similar to reported human values. Adrenal tissue showed significant concentrations of beta-carotene by 24 h post-dosing, and levels were still elevated at 264 h. Liver, spleen and lung beta-carotene concentrations were significantly elevated by 24 h and rapidly declined thereafter. Adipose and kidney peak beta-carotene concentrations were observed at 72 and 144 h, respectively. Heart and muscle did not display significant changes in beta-carotene concentrations. The preruminant calf shows promise as an animal model for the study of absorption and metabolism of carotenoids by humans.

Concentrations of selected carotenoids and vitamin A in human liver, kidney and lung tissue.

Concentrations of preformed vitamin A and five individual carotenoids (alpha-carotene, beta-carotene, cryptoxanthin, lutein and lycopene) were determined in liver, kidney and lung tissue from 20 autopsies of subjects ranging in age from 4 mo to 86 y. Total carotenoid concentrations in liver tissue were always greater than in kidney or lung tissue within the same patient. Total carotenoid concentration in adult subjects was 2.5-77.1 nmol/g tissue (mean 21.0 nmol/g tissue) in liver tissue (n = 14), 0.2-12.7 nmol/g tissue (mean 3.1 nmol/g tissue) in kidney tissue (n = 13) and 0.1-8.4 nmol/g tissue (mean 1.9 nmol/g tissue) in lung tissue (n = 13). Carotenoid content in tissue samples from two infants was low, ranging from 0 to 1.0 nmol/g tissue. beta-Carotene and lycopene were almost always the predominant carotenoids found in liver, kidney and lung tissue. beta-Carotene was positively correlated (P less than 0.05) with alpha-carotene, lycopene and total carotenoids in all of the tissues examined. In addition, beta-carotene and total carotenoids from liver tissue were positively correlated with the same carotenoids in both kidney and lung tissue within each patient. Total vitamin A (free plus esterified) concentration was 8.7-1102.2 nmol/g tissue in liver (n = 17), 3.5-343.9 nmol/g tissue in kidney (n = 14) and 0.7-404.6 nmol/g tissue in lung (n = 14). Vitamin A concentrations were significantly correlated with both beta-carotene and total provitamin A carotenoid concentrations in liver tissue, but not in kidney or lung tissue.

High-performance liquid chromatography and capillary supercritical-fluid chromatography separation of vegetable carotenoids and carotenoid isomers.

Carotenoids from carrots and tomatoes were separated with high-performance liquid chromatography (HPLC) and capillary supercritical fluid chromatography (SFC). All trans alpha- and beta-carotene were separated from their respective cis-isomers with capillary SFC. Carotenoids extracted from tomatoes included xanthophyll, lycopene and beta-carotene, while alpha- and beta-carotene were extracted from carrots. The HPLC separations were accomplished isocratically with a 25-cm column containing 5-microns ODS and methanol-acetonitrile-chloroform (47:47:6) or acetonitrile-dichloromethane (80:20). beta-Carotene cis-isomers were separated with SFC with a SB-cyanopropyl-25-polymethylsiloxane column, while alpha-carotene isomers were separated with two SB-cyanopropyl-50-polymethylsiloxane columns. Carotenoids from carrots and tomatoes were separated with a SB-phenyl-50-polymethylsiloxane column. Carbon dioxide with 1% ethanol was the SFC mobile phase. The eluent was monitored at 461 nm for HPLC and either 453 or 461 nm for SFC.