The role of leukotrienes as mediator of brain edema is still controversial. Recently, the ability of gamma-GTP to act as enzymatic barrier and to inactivate leukotrienes in normal brain capillaries was pointed out. A hypothesis tested in our experiments was that Leukotriene C4 (LTC4) increases permeability of a cerebral capillary endothelial monolayer which lacks gamma-GTP activity. Brain capillary endothelial cells were obtained of 10 rats from cerebral cortex by an enzymatic isolation procedure. The cells have an intact function, however, lack gamma-GTP activity. The endothelial cells were cultured on an optically clear collagen membrane mounted on a plastic frame. Effects of bradykinin (1 x 10(-5) M) and LTC4 (1 x 10(-7) M, 1 x 10(-6) M, 5 x 10(-6) M, 1 x 10(-5) M) were tested on permeability of the endothelial cell monolayer by measuring leakage of 14C-sucrose. The effect of LTC4 and bradykinin on intracellular calcium was studied by laser scanning confocal microscopy. LTC4 did not increase permeability of the brain capillary endothelial cell monolayer which lacked gamma-GTP activity. LTC4 did neither increase the concentration of intracellular calcium. Differences of LTC4 receptor function in normal brain capillaries and tumor capillaries remain to be studied.