title: Mechanisms for vitamin A transfer from blood to milk in rhesus monkeys.
abstract: In order to study vitamin transport during lactation tritium labeled vitamin A, attached to serum lipoproteins or retinol-binding protein (RBP), was injected intravenously into eight Rhesus monkeys. The turnover rate of vitamin A in plasma and its appearance in milk was quantitatively and qualitatively investigated. The turnover of plasma RBP-retinol, which was somewhat faster in lactating than in non-lactating animals, exceeded that of lipoprotein-vitamin A by a factor of three. Tritium--vitamin A appeared in milk mainly as retinylesters. The fractional rate of transfer was about 60% higher for vitamin bound to RBP than for other forms of plasma vitamin A. Consequently, about 90% of the vitamin A appearing in milk will normally be derived from the retinol-RBP complex. The importance of the lipoprotein-mediated transfer of vitamin A will probably increase during a high intake of the vitamin.
mesh_terms: D000818:Animals; D005260:Female; D000882:Haplorhini; D007774:Lactation; D008253:Macaca mulatta; D008892:Milk / Q000378:metabolism*; D011247:Pregnancy; D012177:Retinol-Binding Proteins / Q000097:blood; D054839:Retinol-Binding Proteins, Plasma; D014801:Vitamin A / Q000097:blood / Q000378:metabolism*
chemical_list: D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma; D014801:Vitamin A