Effect of ambient oxygen changes on platelet activating factor production by fetal ovine endothelial cells

To determine whether platelet activating factor (PAF) plays a role in the responses seen in the fetal and transitional circulations, we assessed endogenous release of PAF in cultured fetal ovine endothelial cells from the pulmonary artery (PA), ductus arteriosus (DA) and aorta (Ao) under basal conditions and following exposure to hypoxia or hyperoxia. The cells were prelabeled with [3H] acetate and subsequently exposed to different ambient oxygen concentrations, i.e., 95% O2 or 95% N2, balance CO2, using calcium ionophore as a positive control. The effect of indomethacin on DA endothelial PAF production following stimulation with ionophore was also established. Synthesis of [3H] PAF was measured by counts comigrating on TLC with unlabeled PAF. We found that PAF production by fetal ovine PA, Ao and DA cells was similar and unaffected by hypoxia or hyperoxia. Exposure of ionophore stimulated DA cells to indomethacin was, however, associated with a decrease in PAF production (p less than 0.05). We speculate that in vitro alterations in ambient O2 concentration do not influence fetal ovine endothelial PAF production but indomethacin may decrease PAF production in the DA.