Products of arachidonic acid (AA) metabolism via the lipoxygenase pathways may have key roles in the maintenance of pregnancy and the onset of labor. We have determined whether calcium ionophores can modulate the rate of biosynthesis within the uterus of five important arachidonate lipoxygenase metabolites, i.e. leukotriene B4 (LTB4), LTC4, 5-hydroxyeicosatetraenoic acid (5-HETE), 12-HETE, and 15-HETE. Amnion, chorion, and decidual cells were isolated, grown to confluence and incubated with ionomycin. The production of LTB4, LTC4, 5-HETE, 12-HETE, and 15-HETE was determined using specific radioimmunoassays. Cell-specific, concentration-related stimulatory actions of ionomycin on 5-HETE, 12-HETE, 15-HETE, and LTC4 but not LTB4 production were found. A23187 had effects similar to ionomycin. Hence elevation of intracellular calcium levels can result in enhanced intrauterine production of arachidonate lipoxygenase metabolites that may affect pregnancy outcome.