Biotin-Labled Phosphatidylethanol (Biotin-PEth) can be used to build biological assays testing for serum and in vitro PEth levels. PEth is formed primarily in the liver by transphosphatidylation of phosphatidylcholine (PC) by phospholipase D. PEth is associated with lipoprotein particles VLDL and HDL. PEth-containg HDL/protein complexes may protect against atherogenesis by promoting vascular endothelial growth factor secretion by smooth muscle cells and endothelium. Most PEth (about 75%) is incorporated into erythrocyte membranes, and is the longest-lived circulating ethanol metabolite yet identified.