Purification and identification of very low density lipoprotein toxicity preventing activity

Toxicity preventing activity (TxPA) is a recently identified substance in serum which counteracts the toxic effect of very low density lipoproteins upon endothelial cells in vitro. In two clinical studies, TxPA was low in individuals with angiographically demonstrable coronary artery disease. An atherogenic index which combines TxPA with lipoprotein cholesterol values classifies individuals with coronary artery disease with an accuracy of greater than 93%. TxPA precipitates with 0.15 M trichloroacetic acid and above 3 M (NH4)2SO4. Activity is present in Cohn fractions IV4 and V and is stabilized by antioxidants. TxPA co-elutes with the albumin peak on gel filtration chromatography and as a subcomponent of albumin on ion-exchange chromatography. Isoelectric focusing resolves albumin into two major peaks with pI values of 4.8 and 5.6. The TxPA is identified as the pI 5.6 albumin peak.