Prostaglandin synthesis in rat adrenocortical cells

The biosynthesis of prostaglandins by isolated rat adrenocortical cells has been studied by determinations of products formed during incubations with labeled arachidonic acid and by radioimmunoassays. Analysis by thin-layer chromatographic separation of silicic acid column fractions indicated that PGE2, PGA2, (B2) and PGF2 alpha were the predominant prostaglandins formed by rat adrenocortical cells. Approximately 75% of the incorporated isotope was associated with the prostaglandins of the PGE pathway [PGE2 + PGA2 (B2)]. This was a consistent finding whether cells were incubated directly with arachidonic acid or with cells prelabeled with the substrate prior to study. ACTH did not affect the uptake or oxidation of [1-14C]-arachidonate, but did significantly increase incorporation of labeled substrate into [14C]prostaglandins. Of the ACTH-induced increase, 92% was accounted for by an increase in prostaglandins of the E pathway. Studies with prelabeled cells indicated that 77% of the prostaglandins synthesized in both control and ACTH-stimulated adrenocortical cells was released into the incubation medium during the 2-hr study. These had the same composition [88% PGE2 + PGA2 (B2)] as did the intracellular prostaglandins. Analysis by radioimmunoassays gave comparable data on the distribution of E- and F-type prostaglandins in control cells and cells incubated with ACTH or dibutyryl cyclic AMP. Thus, with these techniques, 88-92% of the increased prostaglandin synthesis due to ACTH or cyclic AMP was produced by the PGE2 rather than the PGF2 alpha pathway.