Dietary beta-carotene absorption by blood plasma and leukocytes in domestic cats

Three experiments were conducted to study the uptake of oral beta-carotene by blood plasma and leukocytes in domestic cats. In Experiment 1, mature female Tabby cats (12 mo old) were given once orally 0, 10, 20 or 50 mg of beta-carotene and blood taken at 0, 12, 24, 30, 36, 42, 48 and 72 h after dosing. Concentrations of plasma beta-carotene increased in a dose-dependent manner. Peak concentrations were observed at 12-24 h and declined gradually thereafter. The half-life of plasma beta-carotene was 12-30 h. In Experiment 2, cats were dosed daily for six consecutive days with 0, 1, 2, 5 or 10 mg beta-carotene. Blood was sampled once daily at 12 h after each feeding. Daily dosing of cats with beta-carotene for 6 d resulted in a dose-dependent increase in circulating beta-carotene. Experiment 3 was designed to study the uptake of beta-carotene by blood leukocytes. Cats were fed 0, 5 or 10 mg of beta-carotene daily for 14 d. Blood leukocytes were obtained on d 7 and 14 to determine beta-carotene content in whole lymphocytes and in subcellular fractions. Blood lymphocytes took up large amounts of beta-carotene by d 7 of feeding. Furthermore, beta-carotene accumulated mainly in the mitochondria (40-52%), with lower amounts accumulating in the microsomes (20-35%), cytosol (15-34%), and nuclei (1.5-6%). Therefore, domestic cats readily absorb beta-carotene across the intestinal mucosa and transfer the beta-carotene into peripheral blood leukocytes and their subcellular organelles. beta-Carotene uptake kinetics show that some aspects of beta-carotene absorption and metabolism in cats are similar to those of humans.