Lipid binding protein (apolipoprotein A-I) contamination of high grade commercial albumins

albumms are frequently used m experiments mvolvlng lipoprotein metabohsm, for mamtaimng oncottc pressure m organ perfusron systems m the study of synthesis and metab- ohsm ofhpoprotems [ l-31 and as acceptors for fatty acids m studies of trrglycende catabolism by hpo- protein hpase (LPL, EC 3 .l .1.34) [3--51 The albumin preparatrons are supposed to be pure and devoid of apohpoprotems, and besides then ability to bmd fatty acids and lysolecithin, to be inert m hprd metab- olism [6]. In the present report we provrde evrdence that some commercially available ‘fatty acid poor’ or ‘fatty acid free’ albumms both of human and bovine orrgm contam apohpoprotem A-I (apo A-I) m appreciable amounts. Apo A-I has been shown to bmd avidly phosphohpids and produce drscordal particles [7], to bind easily to studied lipoproteins [8] and to be the specific cofactor for one of the key enzymes m lipoprotem metabolism, lecithin : cholesterol acyl transferase (LCAT, EC 2 3 1.43) [9]. Therefore, the use of such albumrn preparations m the study of hpoprotems may interfere with the mterpretatton of such experiments. We wish to caution against the use of commercral albumins m hpoprotem metabolism studies prior to quantifying apo A-I m them