Metabolism of apolipoprotein A-I in healthy young adults

The metabolism of 125I-labeled apolipoprotein A-I bound to high-density lipoproteins by an in vitro transfer procedure was studied in 10 healthy young adults (5 males and 5 females). Both sexes handled the labeled apolipoprotein similarly, and no statistically significant differences were found in the derived kinetic data. The mean (+/- 1 SD) plasma apolipoprotein A-I concentrations (males, 105 +/- 19 mg/dl; females, 111 +/- 13.8 mg/dl) and half-lives (males, 4.46 +/- 0.45 days; females, 4.64 +/- 0.70 days) were similar, as were the fractional rates of catabolism (FCR) of the apoprotein derived from the above data (FCR in males, 27% of intravascular pool/day; FCR in females, 25% of intravascular pool/day). The absolute catabolic rate of the apoprotein, equivalent under steady-state conditions to the synthetic rate, was 12.1 +/- 1.6 mg/kg/day in males and 11.9 +/- 2.4 mg/kg/day in females.