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The cellular origin of prostaglandins in human tumors was investigated using cell fractionation procedures and high resolution gas chromatography. Additionally, the role of macrophages and prostaglandins on human tumor cloning in vitro was investigated. Spontaneous human tumors were prepared as single cell suspensions which were subsequently manipulated to yield macrophage-enriched, and tumor cell enriched (macrophage-depleted) subpopulations of cells. A fused silica capillary gas chromatographic analysis with electron capture detection was developed to measure derivatized prostaglandins in the supernatant of the cell subpopulation incubations. The derivative used for the analysis was the pentafluorobenzyl ester-methoxime-trimethyl-silyl ether. The assay showed a detection limit of 25 picograms of prostaglandins E₁, E₂, F₂ₐ, and I₂ (which was detected as 6-Keto-PGF₁ₐ). Analysis of cell subpopulations of seventeeen tumor samples showed that the macrophage-enriched cells were responsible for the large majority of prostaglandin production in vitro (p ≤ 0.02). It was found that the major prostaglandins were PGE₂ and PGI₂. The range of values measured for macrophage produced prostaglandin E₂ was 1.1 to 704.8 ng/ml after a 24 hour incubation of 10⁶ cells. Prostaglandin I₂ was also produced by the macrophage-enriched cell subpopulation with values ranging from 1.2 to 334.3 ng/ml. This is the first report of prostaglandin I₂ production by host macrophages infiltrating human tumors. Studies of the effect of macrophage depletion and reconstitution on the ability of tumor cells to form colonies in vitro were performed. A two layer soft agar assay was used to evaluate tumor cells clonogenicity. The results demonstrated that macrophages infiltrating human carcinoma samples function in a supportive role for tumor cell colony formation in vitro. Using a prostaglandin synthesis inhibitor, flurbiprofen, it was shown that this support was not the result of a direct effect of prostaglandins on the tumor cells. Possible roles for macrophage produced prostaglandins in cancer are discussed.

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Exogenous prostaglandins (PGs) have been reported to suppress or to promote the function of the primate corpus luteum in vitro and in vivo, but the role of endogenous ovarian prostaglandins in regulating luteal function during the menstrual cycle is unknown. Infusion (via osmotic pump) of the prostaglandin-synthesis inhibitor sodium meclofenamate into the corpus luteum, but not via the jugular vein, during the midluteal phase of the menstrual cycle resulted in a decline in progesterone levels and premature menses in rhesus monkeys (Macaca mulatta). These results suggest that meclofenamate suppresses the production of an obligatory luteotropic prostaglandin or other metabolite of arachidonic acid. We were unable to confirm that ovarian prostaglandin synthesis was diminished during treatment, since we could not consistently measure a gradient in PGE or PGF₂(α) across the ovary. Dispersed cells from the macaque corpus luteum produced PGF₂(α) in vitro. Production was stimulated by exposure to arachidonic acid and was inhibited by meclofenamate and another prostaglandin-synthesis inhibitor, flurbiprofen. Although the two drugs were potent inhibitors of prostaglandin synthesis in vitro, intraluteal infusion of flurbiprofen in monkeys did not mimic the luteolytic effects of meclofenamate. These studies provide the first evidence of an obligatory luteotropic role for a metabolite of arachidonic acid during the primate luteal phase. However the data suggest that the luteolytic effect of meclofenamate in vivo is not mediated entirely by the inhibition of local prostaglandin synthesis. Further studies are needed to determine the mechanism(s) of meclofenamate-induced luteolysis and to identify the putative obligatory luteotropin.

Prostaglandin G/H synthase-2 (PGHS-2) is a key rate limiting enzyme in the prostaglandin (PG) biosynthetic pathway, and PG synthesis is required for ovulation in pigs. The objective of this study was to characterize the expression and regulation of PGHS-2 in porcine follicles prior to ovulation. The combination of equine chorionic gonadotropin (eCG; 750 IU) followed by human chorionic gonadotropin (hCG; 500 IU) 72 h later was used to induce ovulation in prepubertal gilts. Previous studies have shown that ovulation is generally induced between 40 and 44 h post-hCG in this model. Ovariectomies were performed at 0, 24, 30, 34 and 38 h post-hCG (n = 4 or 5 animals per time-point), and all follicles larger than 4 mm in diameter were isolated. The regulation of PGHS-1 and PGHS-2 proteins was studied by immunohistochemistry and Western blot analyses, whereas the regulation of PGHS-2 mRNA was studied by Northern blot. PG production was assessed by radioimmunoassay (RIA). (Abstract shortened by UMI.)

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