Adipose differentiation related protein (ADRP) is a 50-kDa novel protein cloned from a mouse 1246 adipocyte cDNA library, rapidly induced during adipocyte differentiation. We have examined ADRP function, and we show here that ADRP facilitates fatty acid uptake in COS cells transfected with ADRP cDNA. We demonstrate that uptake of long chain fatty acids was significantly stimulated in a time-dependent fashion in ADRP-expressing COS-7 cells compared with empty vector-transfected control cells. Oleic acid uptake velocity increased significantly in a dose-dependent manner in ADRP-expressing COS-7 cells compared with control cells. The transport Km was 0.051 microM, and Vmax was 57.97 pmol/10(5) cells/min in ADRP-expressing cells, and Km was 0.093 microM and Vmax was 20.13 pmol/10(5) cells/min in control cells. The oleate uptake measured at 4 degrees C was only 10% that at 37 degrees C. ADRP also stimulated uptake of palmitate and arachidonate but had no effect on uptake of medium chain fatty acid such as octanoic acid and glucose. These data suggest that ADRP specifically enhances uptake of long chain fatty acids by increasing the initial rate of uptake and provide novel information about ADRP function as a saturable transport component for long chain fatty acids.