Effects of Oxygen, Calcium Ionophore, and Arachidonic Acid on Prostaglandin Production by Monolayer Cultures of Mixed Cells and Endothelial Cells from Rat Fetal Lungs

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Abstract
Prostaglandins (PGs) synthesized by fetal and neonatal lungs play pivotal roles in pulmonary physiology, especially during the transition from uterine to independent life. One regulator of prostaglandin synthesis at this time may be oxygen. We examined the effects of 1% O2, 21% O2 and 50% O2 in 5% CO2, balance N2 (PO2 values in medium = 30 .+-. 4, 142 .+-. 4, and 260 .+-. 3 mm Hg, respectively), on prostaglandin production from monolayer cultures of mixed or endothelial cells prepared from day 20 gestation rat fetal lungs. Cells were untreated or stimulated to produce prostaglandins by the addition of the calcium ionophore, A23187 (10-5 M), or the prostaglandin precursor, arachidonic acid (AA, 1 .mu.g/ml). Prostaglandins 6-keto F1.alpha. (6KF; the hydrolysis metabolite of prostacyclin, PGI2), E2, F2.alpha. and 13,14-dihydro-15-keto PGF2.alpha. (FM, the enzymatic metabolite of PGF2.alpha.) were measured by radiommunoassay. The basal release of 6KF from mixed cells into serum-free medium was approximately 2 ng/106 cells/3 days. The levels of 6KF were 10-fold greater than those of the other prostaglandins. Basal endothelial cell release of 6 KF was 30 ng/106 cells/3 days, and this was 15- to 100-fold greater than that of the other prostaglandins measured. In mixed cells, oxygen treatment for 3 days had no effect upon the basal release of any prostaglandin, nor was there any effect of oxygen upon the basal 6KF or PGE2 production in endothelial cells. However, both PGF2.alpha. and PGFM production by endothelial cells was decreased (p < 0.05) in 50% O2 compared to 1% O2. Both A23187 and AA enhanced prostaglandin release from mixed and endothelial cells. Ionophore-stimulated 6KF net production in mixed cells was greater in 21% O2 than in 1% O2 (p < 0.05). Calcium ionophore stimulated the net production of 6KF and PGE2 in endothelial cells in 21% O2 versus 1% O2 (P < 0.05), and AA enhanced the net production of 6KF, PGE2 and PGF2.alpha. in endothelial cells in 21% O2 versus 1% O2. We conclude that rat fetal pulmonary cells produce prostaglandins from endogenous and exogenous substrates, that prostaglandin production is sensitive to Ca2+-mobilizing agents, and that the production of the vasodilators PGI2 and PGE2 increases in the presence of 21% O2 and a stimulating factor.