COS-7 cells transfected with the leukotriene (LT) B4 receptor (BLTR) cDNA were unable to produce LTB4-induced inositol phosphates (IPs) in spite of the presence of endogenous Galphai, Galphaq and Galpha11 proteins. Co-transfection of BLTR with Galpha16, however, resulted in high levels of IP production, which were 17-, 10- and 6-fold higher than with co-transfected Galpha11, Galphaq and Galpha14, respectively. Co-transfection of BLTR with phospholipase C (PLC) beta2, on the other hand, resulted in efficient IP production and co-transfection of BLTR with both Galpha16 and PLCbeta2 resulted in a greater than additive response.