In vivo metabolism of apolipoprotein S in humans. Comparison with apolipoprotein A-I metabolism.
125I-labelled apolipoprotein (Apo) S and 131I-labelled apolipoprotein A-I were injected i.v. into healthy volunteers. Blood samples and daily urine collections were drawn periodically for 15 days. Ninety-eight percent of 131I radioactivity and greater than 95% of 125I radioactivity were found in HDL after Superose gel chromatography of plasma. About 10% of each radioactivity was recovered in the d 1.250 infranate after one ultracentrifugation. Affinity chromatography on monoclonal anti-Apo A-I Sepharose column separates two lipoprotein particles containing Apo S, one retained with Apo A-I (42.5%) and the other eluting without Apo A-I (57.5%). Kinetic parameters were calculated according to exponential curve fitting. Mean transit time was about 7.0 days for both Apo A-I and Apo S. FCR of Apo S was 50% higher than FCR of Apo A-I. Synthetic rate of Apo S was about 150 times smaller than for Apo A-I. As heterogeneity of HDL-S was suggested by both the results of affinity chromatography and the urinary data, a compartmental model was built which fitted adequately all data. Part of the model is common to HDL-A-I and HDL-S.
D000328:Adult; D016632:Apolipoprotein A-I; D001053:Apolipoproteins / Q000378:metabolism*; D001054:Apolipoproteins A / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008297:Male; D012016:Reference Values
D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D001054:Apolipoproteins A; D008075:Lipoproteins, HDL; C029798:apolipoprotein S-peptides