Previous studies with alcohol-associated malondialdehyde-acetaldehyde (MAA)-modified proteins have demonstrated an increase in the expression of adhesion molecules, and the secretion of pro-inflammatory cytokines/chemokines by rat sinusoidal liver endothelial cells (SECs). However, no studies have been initiated to examine the effects of MAA-modified proteins on the expression of the extracellular matrix (ECM) protein, fibronectin and its isoforms. For these studies, SECs were isolated from the liver of normal rats, and exposed to MAA-modified bovine serum albumin (MAA-Alb). At selected time points, the total plasma and cellular fibronectin were determined by Western blot. Injection of rat liver via the mesenteric vein with MAA-Alb was performed in an effort to evaluate the potential in vivo role of MAA-modified proteins in the development of fibrosis. Expression of both plasma and cellular fibronectin was significantly increased over controls in the MAA-Alb stimulated SECs (>3-fold). Importantly, the isotype of fibronectin secreted was determined to be of the EIIIA variant and not EIIIB. These data were confirmed using RT-PCR procedures on liver tissue from; isolated SECs, and from an in vivo animal model wherein MAA-Alb was administered via the mesenteric vein. Thus, these studies demonstrate that MAA-modified proteins initiate a pro-fibrogenic response by initiating the expression of the fibronectin EIIIA isoform by SECs.