UPTAKE OF ORALLY-ADMINISTERED BETA-CAROTENE BY BLOOD-PLASMA, LEUKOCYTES, AND LIPOPROTEINS IN CALVES

The uptake of beta-carotene by blood cells, plasma, and lipoproteins was studied in bull calves that were orally administered a single (Exp. 1; n = 18 Angus calves) or multiple (Exp. 2; n = 16 Holstein calves) doses of beta-carotene. Administration of beta-carotene increased plasma beta-carotene and the amount of beta-carotene associated with each lipoprotein fraction. Before beta-carotene treatment, the total amount of beta-carotene associated with the high-density lipoprotein (HDL) was three- to fourfold higher than the amount associated with low-density lipoprotein (LDL) and fivefold higher than the amount associated with very-low-density lipoprotein (VLDL). The relative increase in total beta-carotene associated with the lipoproteins was greater for LDL than for HDL or VLDL. Orally administered beta-carotene increased the uptake of beta-carotene by lymphocytes. Subcellular fractions of blood lymphocytes isolated from animals fed beta-carotene revealed that beta-carotene was taken up in significant amounts by the mitochondrial, nuclear, and microsomal fractions. The profile of beta-carotene uptake by these subcellular fractions did not mirror that observed in plasma. In contrast, beta-carotene was not detectable in blood neutrophils and erythrocytes in either beta-carotene-supplemented or unsupplemented calves. Treatment did not influence the concentrations of retinol or alpha-tocopherol in plasma, lipoproteins, lymphocytes, neutrophils, or erythrocytes. These data revealed the presence of beta-carotene in bovine lymphocyte subcellular fractions and suggest a possible physiological role of beta-carotene in these cells.