Distribution of orally administered beta-carotene among lipoproteins in healthy men.

Plasma and lipoprotein concentrations of beta-carotene (BC) were measured in men for 10 d after an oral dose of BC (120 mg) (experimental subjects, n = 11) or no BC (control subjects, n = 5). Lipoproteins were separated by sequential ultracentrifugation and BC was measured by HPLC. Plasma and lipoprotein BC concentrations in control subjects were steady. In experimental subjects, plasma BC content increased by 6 h postdosing (P less than 0.015), peaked at 24 h (P less than 0.05), and returned to baseline by 7 d. Maintenance of plasma BC concentrations suggests homeostatic control. Of the 11 experimental subjects, only 4 had a plasma response. Early increases in the BC content of chylomicrons, very-low-density lipoproteins, and intermediate-density lipoproteins. Intestinal input accounts for early rises in circulating BC concentrations whereas hepatic secretion is the source of later increases. Among all of the lipoproteins, transfer of BC may occur.