Measurement of prebeta-1 HDL in human plasma by an ultrafiltration-isotope dilution technique.
Prebeta-1 HDL is a 67-kDa species of plasma high-density lipoproteins (HDL) that contains two copies of apolipoprotein A-I. It functions in a metabolic cycle of cholesterol retrieval and may be formed during lipolysis in plasma. We have found that centrifugal ultrafiltration using a membrane with a permeability limit of 100 kDa discriminates categorically between the 67-kDa species and larger HDL particle species. Thus, the ultrafiltrate samples the pool of prebeta-1 HDL in plasma. We have developed a technique using the dispersal of purified prebeta-1 HDL, labeled covalently with tritium, in plasma samples, to label the prebeta-1 HDL pool. Subsequent determination of the specific activity of prebeta-1 HDL in the ultrafiltrate provides a means of calculating the content of prebeta-1 HDL in plasma by the isotope dilution principle. We employ a modification of an enzyme-linked immunosorbent assay technique for apolipoprotein A-I that allows the equal detection of that protein in prebeta-1 HDL and in other HDL particle species for determination of the fraction of total apolipoprotein A-I that is present in the prebeta-1 HDL particle species. The mean level of prebeta-1 HDL-associated apolipoprotein A-I in plasma samples from 86 normolipidemic adults was 74 +/- 43 microg/ml (+/-SD), representing an average of 6.6% of the total apolipoprotein A-I in plasma.
O'Connor
P M
PM
Cardiovascular Research Institute, University of California, San Francisco, California 94143-0130, USA.
Naya-Vigne
J M
JM
Duchateau
P N
PN
Ishida
B Y
BY
Mazur
M
M
Schoenhaus
S A
SA
Zysow
B R
BR
Malloy
M J
MJ
Kunitake
S T
ST
Kane
J P
JP
D000328:Adult; D016632:Apolipoprotein A-I / Q000097:blood*; D053442:High-Density Lipoproteins, Pre-beta; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood*; D011865:Radioisotope Dilution Technique; D014316:Tritium; D014462:Ultrafiltration / Q000379:methods*
D016632:Apolipoprotein A-I; D053442:High-Density Lipoproteins, Pre-beta; D008075:Lipoproteins, HDL; D014316:Tritium