In vivo metabolism of apolipoproteins A-IV and A-I associated with high density lipoprotein in normolipidemic subjects.
The kinetics of apolipoprotein A-IV associated with high density lipoproteins (HDL) of plasma from fasting human subjects was followed for 15 days in five healthy normolipidemic volunteers. Purified apoA-IV and apoA-I were radioiodinated, respectively, with 125I and 131I, incubated in vitro with normal HDL, isolated at density 1.250 g/ml, and finally reinjected intravenously as HDL-125I-labeled apoA-IV and HDL-131I-labeled apoA-I. Blood samples were withdrawn at regular intervals for 15 days, and 24-h urine samples were collected. More than 93% (93.5 +/- 0.9%) of apoA-IV was recovered in apoA-I-containing lipoprotein particles after affinity chromatography on an anti-apoA-I column and 69.7 +/- 4.8% was bound to apoA-II in apoA-I:A-II particles separated on an anti-apoA-II column. 125I-labeled apoA-IV showed a much faster decay than 131I-labeled apoA-I for the first 5 days and thereafter the curves became parallel. Urinary/plasma ratios (U/P) for the 125I-labeled parallel. Urinary/plasma ratios (U/P) for the 125I-labeled apoA-IV were much higher than those for 131I-labeled apoA-I for the first days, but the U/P curves became parallel for the last 7 days, suggesting heterogeneity of apoA-IV metabolism. A heterogeneous multicompartmental model was constructed to describe the metabolism of lipoprotein particles containing apoA-IV and apoA-I and to calculate the kinetic parameters, fitting simultaneously all plasma and urine data for both tracers.(ABSTRACT TRUNCATED AT 250 WORDS)
Malmendier
C L
CL
Fondation de Recherche sur l'Athérosclérose, Brussels, Belgium.
Lontie
J F
JF
Lagrost
L
L
Delcroix
C
C
Dubois
D Y
DY
Gambert
P
P
D000328:Adult; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000097:blood* / Q000652:urine; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008075:Lipoproteins, HDL / Q000097:blood*; D008297:Male; D008954:Models, Biological
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D007457:Iodine Radioisotopes; D008075:Lipoproteins, HDL; C022205:apolipoprotein A-IV