The role of serum fatty acid binding proteins (FABPs) in arachidonic acid (AA) uptake by murine peritoneal macrophages has been studied. The kinetics of [H-3]arachidonic acid uptake by the cells was investigated over a wide range of AA concentration (10(-10)-10(-5) M). It was shown that these putative fatty acid transporters dramatically change the uptake processes. In the presence of FABPs, the time-course curves of AA uptake exhibited two distinct periods: one with a rapid AA uptake during the first hour with an equilibrium in 1-2.5 h and another with an equilibrium reached in 20 h, whereas in the absence of FABPs the uptake curves were smooth without kinks and with the equilibrium reached in 10 h. In addition, it was shown that the amount of incorporated AA was Linearly dependent on the concentration of AA over the range of 10(-10)-10(-6) M in the presence of serum FABPs and 10(-10)-10(-7) M in their absence. We assume that the changes in the character of AA uptake by macrophages in the presence of FABPs occur due to the interaction of FABPs with the cell plasma membrane.