SEX-DIFFERENCES IN POSTABSORPTIVE PLASMA VITAMIN-A TRANSPORT

This study examined postabsorptive plasma vitamin A after doses of retinyl palmitate in healthy men (n = 28) and women (n = 31). On consecutive days one physiologic [3000 retinol equivalents (RE)] and one pharmacologic dose (105 000 RE) were administered and blood samples collected. Plasma retinol and retinyl esters were measured by HPLC. Tolerance curves were constructed by plotting plasma retinyl ester concentration vs time. Postprandial retinyl ester response was measured as peak rise in retinyl ester concentration and area under the curve (AUC). Peak plasma retinyl ester concentration occurred earlier for females but the earlier peak was significant only for younger subjects (less-than-or-equal-to 50 y, P < 0.02) given the low dose and older subjects (> 50 y, P < 0.02) given the high dose. Peak rise and AUC were lower in females than in males, but this difference was significant for the high dose only (P < 0.05). In the high-dose experiment, when each age group was evaluated for sex differences the peak rise was significantly greater in males than in females in the older subjects (P < 0.05). Postabsorptive plasma retinol did not change from fasting concentrations. A lower plasma response in retinyl esters in women could be due to a more efficient chylomicron-remnant clearance.