6-keto PGF1α Research Articles

Biosynthesis of prostaglandins by human spermatozoa in vitro and their role in acrosome reaction and fertilization.

Five homogenates of human sperm cells were separately incubated with [14C]arachidonic acid in the presence of reduced glutathione, L-tryptophan, and haematin as cofactors. The cyclooxygenase products of arachidonic acid metabolism were extracted, separated, and measured for their radioactivity. The rate of formation of prostaglandin (PG)D2, PGE2, PGF2 alpha, 6-keto PGF1 alpha, and thromboxane (TX)B2 were 18.0 +/- 1.11, 10.9 +/- 0.68, 5.8 +/- 0.21, 3.9 +/- 0.13 and 6.6 +/- 0.52 pmol/10(6) cells/min, respectively. These results are discussed in relation to the hypothesis that cyclooxygenase metabolites of certain polyunsaturated fatty acids play an important part in the sperm acrosome reaction and fertilization.

Independent regulation of prostaglandin production and the stress response in human fibroblasts.

The stress, or heat shock response of eukaryotic cells is characterized by dramatic changes in the metabolism of responding cells, most notably the increased synthesis of a group of proteins known as heat shock proteins. In this study, we examined the relationship of prostaglandin synthesis/release to the stress response. Stress protein synthesis was induced with sodium arsenite, and prostaglandin E2 and prostacyclin (measured as 6-keto PGF1 alpha) levels were determined by enzyme immunoassay. The stress response was monitored by the incorporation of [35S]methionine and separation of protein by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Prostaglandin synthesis and the stress response were both induced by sodium arsenite. However, aspirin, a cyclooxygenase inhibitor, inhibited arsenite-induced prostaglandin synthesis but did not inhibit stress protein synthesis. Conversely, the calcium ionophore A23187 also stimulated prostaglandin synthesis, but did not induce the stress response. The results of this study indicate that sodium arsenite, a stress response inducer, stimulates prostaglandin production, but this appears to be a correlative rather than causative occurrence in the stress response. Determination of the cytotoxicity of arsenite indicated a high correlation of stimulation of prostaglandin release with cytotoxicity.

Prostaglandin E production by uteri of ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn

Antiprogesterone steroid, ZK98299 (Schering, Germany) or RU38486 (Roussel Uclaf, France), has been administered to ovariectomized early pregnant rats receiving continuous steroid replacement. At 24 h later, uterine explants of rats treated with ZK98299 produced significantly greater amounts of prostaglandin E (PGE) than did controls or animals treated with RU38486. The PGE/PGF 2α production ratio for uteri of rats treated with ZK98299 or RU38486 was markedly lowered compared to controls, and a significant decrease occurred in the PGE 6 -keto PGF 1α production ratio for rats treated with RU38486. For ovariectomized early pregnant rats in which progesterone has been withdrawn, a significant reduction in uterine PGE production occurred when compared to control animals. There was also a marked decrease in PGE/PGF 2α production ratio, and the PGE 6 -keto PGF 1α production ratio tended to be lowered relative to controls. The stimulated production (as by ZK98299) or unchanged production of PGE (as by RU38486) indicates a selective action on uterine PGE synthesis among the antiprogesterone steroids, and these findings cannot be explained simply in terms of a blockage of progesterone receptors.

Effect of Ethanol on the Release of Prostaglandins from Ovine Fetal Brain Stem during Gestation

Prostaglandins (PGs) have been implicated as mediators of the ethanol-induced suppression of ovine fetal breathing movements (FBM). The objectives of the present study were to determine the ontogeny of the in vitro efflux of PGE2 and 6-keto PGF1 alpha in ovine fetal brain stem during the second half of gestation and to determine the effect of in vitro ethanol exposure on the efflux of these PGs. Ovine fetal brain stem tissue was obtained at mean gestational ages of 80 days (n = 6), 105 days (n = 10), and 135 days (n = 16) by rapid excision following maternal euthanization. Tissue slices (400 microM thickness) were prepared from the lower pons-medulla region of the brain stem. After a 1-hr equilibration period in artificial cerebrospinal fluid, efflux of PGE2 and 6-keto PGF1 alpha in the brain stem was determined using the brain slice-superfusion method, and the PGE2 and 6-keto PGF1 alpha concentrations in the superfusate were determined by specific radioimmunoassay. The mean spontaneous efflux of PGE2 and 6-keto PGF1 alpha expressed as pmol PG/gram wet weight of tissue/5-min collection period was, respectively, 31.9 +/- 4.2 and 26.6 +/- 2.4 at 80 days, 38.3 +/- 5.2 and 29.6 +/- 2.2 at 105 days, and 57.4 +/- 3.1 and 27.1 +/- 1.1 at 135 days of gestation. In vitro exposure to 20, 40, and 80 mM ethanol did not affect PG efflux in the brain stem at 80 and 105 days of gestation. In vitro ethanol exposure decreased PGE2 and 6-keto PGF1 alpha efflux at 135 days of gestation to 36.8 +/- 5.3% and 41.6 +/- 4.3% of spontaneous efflux within 15 min, respectively; this effect of ethanol was not dose-dependent. The data do not support the hypothesis that ethanol increases PG efflux in the ovine fetal brain stem. In view of these findings and the data implicating PGs in the mechanism of ethanol-induced suppression of FBM, it is possible that ethanol acts at either central sites rostral to the brain stem (i.e., upstream CSF) or peripheral sites to increase the synthesis of PGs and their efflux into the systemic circulation, with subsequent transfer to the respiratory control region(s) of the brain stem.

Pancreas prostanoid production in ischemia and reperfusion

This study was carried out to investigate the proprtion of the 6-keto prostaglandin F 1α (6-keto PGF 1α) and thromboxane B 2 (TXB 2) alteration that is due to ischemia in pancreas transplantation against the proportion due to reperfusion. For this purpose, Lewis rats were divided in three experimental groups: Group I=Control, Group II=Donor pancreas subjected to 15 minutes of cold ischemia, Group III=Same as group II but pancreas were transplanted to the recipient individual and then subjected to reperfusion. The results indicate that increases in pancreas 6-keto PGF 1α occur as a consequence of cold ischemia while TXB 2 remains unchanged. When blood flow was restored, 6-keto PGF 1α remained unchanged compared to the cold ischemic group while pancreatic levels of TXB 2 were significantly increased. These results suggest a different induction of prostanoid metabolism during ischemia and reperfusion in pancreatic tissue.

Concurrent C18 Solid Phase Extraction of Platelet Activating Factor (PAF) and Arachidonic Acid Metabolites

Abstract Concurrent solid phase extraction of arachidonic acid metabolites and platelet activating factor in human vein umbilical endotelial incubates has been achieved on commercial C18 reversed phase cartridges. Control of sample pH, elution solvents and C18 adsorbent material are important for selective recoveries. Samples were acidified at pH=4.0 and processed through the C18 cartridges which were washed with 10 ml of water/methanol 9/1,10 ml of water at pH=4.0 and 20 ml of petroleum ether. Arachidonic acid metabolites and platelet activating factor adsorbed on the solid phase material were sequentially separated by elution with 4.5 ml of methyl formate and 4.5 ml of methanol, respectively. Recoveries thus obtained were 65.0 ± 2.5%, 89.1 ± 4.6%. 91.1 ± 7.5%, 94.8 ± 1.6 % for PAF, 6-keto PGF1α, 15-HETE and PGE2 respectively. The method was also compared with the classical Bligh & Dyer liquid-liquid extraction procedure.

Prostacyclin—Thromboxane Ratio as a Noninvasive Screening Test for Pulmonary Embolism

The effect of pulmonary embolism (PE) on prostacyclin (PGI2) and thromboxane A2 (TxA2) levels and PGI2- TxA2 ratio (PTR) was investigated in a series of canine experiments. Group I dogs (n = 8) underwent experimental PE with autologous clot. Group II dogs (n=8) received imidazole (30 mg/kg), five minutes before PE to inhibit thromboxane synthesis and to simulate antiplatelet drug therapy. Group III dogs (n=8) received only imidazole without PE. In Groups I and II, PGI2 levels (measured as the 6-keto PGF1α metabolite) increased significantly after PE (p < 0.05), whereas they were not altered in Group III. PE caused a sharper increase in TxA2 levels (measured as the thromboxane B 2 metabolite) in Group I (p < 0.001). Imidazole decreased TxA 2 levels both in Groups II and III (p < 0.05). The reference values (ie, before PE and before imidazole) of PTR were not significantly different among the three groups: 3.8±0.4 in Group I, 3.6±0.2 in Group II, and 3.8 ±0.1 in Group III (mean 3.7±0.2). In Group I, PE resulted in a decrease in the PTR (p < 0.05), which reached its peak significance at ten minutes (from 3.8±0.4 to 1.8±0.2). Imidazole-treated groups showed a significant increase in the PTR irrespective of PE (p < 0.05) by virtue of the decreased thromboxane B2 values. It is concluded that, a PTR ratio of 2 or less is suggestive of PE in patients who do not receive antiplatelet therapy.

Glutathione depletion and rabbit renal medulla 6-ketoPGF 1α and TxB 2: Levels in vivo and following homogenate incubation in vitro

1. 1. The effect of glutathione (GSH) depletion on rabbit renal medullary homogenate 6-ketoPGF 1α and TxB 2 synthesizing capability was investigated. 2. 2. GSH depletion in vivo with diethyl maleate (DEM) produced higher ( P < 0.05) 6-ketoPGF 1α and TxB 2 renal medullary levels compared to controls. Homogenization and incubation lowered ( P < 0.05) GSH such that there were no differences in GSH between treatments after 5 min of incubation. By 30 min, GSH was lower ( P < 0.05) and 6-ketoPGF 1α higher ( P < 0.05) in homogenates from controls in comparison to those from DEM-treated rabbits. 3. 3. The results indicate GSH depletion increased 6-ketoPGF 1α levels in rabbit renal medulla in vivo but subsequent GSH catabolism prevented assessing the effect of this GSH depletion on prostanoid synthesizing capability.

Effect of glutathione depletion on tissue and plasma prostacyclin and thromboxane in rats

Experiments were designed to determine the effects of glutathione (GSH) depletion with l-buthionine sulfoximine (BSO) or diethyl maleate (DEM) on tissue and plasma prostacyclin (6-ketoPGF 1α) and thromboxane (TxB 2) levels in male Sprague-Dawley rats. Despite depleting hepatic GSH to as much as 34% of control, BSO at various levels (0.4, 0.8 and 1.2 g/kg body wt) had no effect on hepatic, renal, pulmonary or cardiac tissue levels of 6-ketoPGF 1α and TxB 2 or circulating levels of 6-ketoPGF 1α in portal or arterial plasma. When rats were pretreated with 3-methylcholanthrene (3-MC) to induce cytochrome P450, BSO (0.8 g/kg body wt) also had no effect on tissue or plasma prostanoid levels with the exception of a slight, but significant, increase in hepatic 6-ketoPGF 1α in non-induced rats. In contrast, depletions of hepatic, renal and pulmonary tissue GSH by DEM (1 mL/kg body wt) to 12, 50 and 30% of control, respectively, were associated with elevations of 6-ketoPGF 1α in these tissues and in plasma obtained by right ventricular heart puncture. Pretreatment of rats with 3-MC had no significant effect on tissue GSH or prostanoid levels in controls or DEM-treated rats but plasma levels of 6-ketoPGF 1α were lower in comparison to non-induced rats. DEM with or without 3-MC pretreatment was associated with increased TxB 2 in renal tissue, whereas DEM elevated TxB 2 only in pulmonary tissue from non-induced rats. It appears that factors besides GSH depletion may be required to raise plasma and/or tissue 6-ketoPGF 1α levels in vivo.

In vitro platelets/endothelial cells interactions in presence of acetylsalicylic acid at various dosages

Venous endothelium is able to release in vitro substances which modifies platelet aggregation. A vascular fragment incubated in Michaelis buffer (pH 7.30), aliquoted and tested on platelet-rich-plasma partially inhibits the aggregometry parameters. Addition of acetylsalicylic acid (ASA) at ultra low dose (0.1 nM final solution in the incubation tube) presents a reversed effect on this inhibition. To explain this phenomenon, 6- keto-PGF 1α and von Willebrand factor were dosed in the incubation media. After determination of an active level of 6-keto-PGF 1α (200 pg/100μl), 2 series were made: series 1 included the values below 200 pg/100μl incubation media, series 2 , the values above 200 pg/100μl incubation media. When the vascular fragment was incubated as described above, the results of aggregometry ratio for series 1 were: test A (without ASA): 0.84±0.18, test B 1 (with 0.1 nM of ASA):0.87±0.13. For series 2 , they became: test A: 0.75±0.27, test B 1: 0.93±0.16. Control was always: 1.00± 0.00. For the same groups, 6-keto-PGF 1α values were: for series 1 , test A:81±57, test B 1:81±60 pg/100μl incubation medium, for series 2 , test A: 596±495, test B 1: 383±263 pg/100 μl incubation medium. Analyses were also performed with 2 high doses of ASA (B 2: 10 5 nM and B 3: 10 6 nM final solution) in the same experimental conditions. In these groups, aggregation parameters were decreased (0.86±0.14 for 10 5 nM, 0.84±0.15 for 10 6 nM) as well as 6-keto-PGF 1α production (189±199 for 10 5 nM, 152±182 for 10 6 nM). For these two last ASA treatments, comparison of the results in groups set up according to the sensitive 6-keto-PGF 1α value (200 pg/100μl solution) showed no modification. So it seems that a certain reactive state, specific of ultra low dose treatment is necessary for the vascular endothelium to be sensitive at such treatment.

Effect of diethyl maleate on glutathione, hepatic and renal cortical perfusion, and portal 6-ketoPGF 1α and TxB 2 levels in swine

1. Effects of diethyl maleate (DEM) mediated glutathione (GSH) depletion on hepatic and renal cortical blood flow (perfusion), plasma GSH, and portal prostacyclin (6-ketoPGF 1α) and thromboxane (TxB 2) were determined in anaesthetized swine. 2. Although DEM depleted hepatic GSH to 25% of control, plasma GSH increased 10-fold in comparison to controls. DEM caused a drop in blood pressure and renal cortical perfusion but had no effect on hepatic perfusion or portal 6-ketoPGF 1α or TxB 2 levels. 3. Possibly, the unexpected rise in plasma GSH may have inhibited prostanoid synthesis, preventing any alterations in tissue perfusion that may have occurred following tissue GSH depletion.

Circadian rhythm in prostacyclin activity in gastric tissue of the fasting rat

Gastroduodenal ulcer disease may result from the desynchronization of the circadian rhythms of gastric protective and destructive factors. The purpose of this study was to evaluate whether gastric tissue 6-keto prostaglandin F1α (PGF1α) catabolic derivative of the putative protective factor prostacyclin, is produced in a circadian fashion in the rat model. Forty-eight male Sprague-Dawley rats were acclimatized in sound-attenuated, lightproof chambers for 3 weeks on a 12:12 hour light/dark entrainment schedule. After an 18-hour fast, six rats were killed at each of eight sampling times. The stomachs were exposed, remove and assayed for total 6-keto PGF1α content by radioimmunoassay. Cosinor analysis of the data showed significant (p = 0.0262) circadian rhythmicity in 6-keto PGF1α content with an acrophase (peak time) value of 0503 HALO (hours after lights on) or in the middle of the lights-on inactive period for the rats. Hypothetically, the circadian rhythm in some gastric protective factors may render the gastric mucosa vulnerable to injury in a circadian fashion.

Cyclosporin reduces renal prostanoid excretion in type 1 diabetic patients.

Prostacyclin and thromboxane A2 are important regulators of kidney blood flow. To examine whether changes in their metabolism could be involved in the nephrotoxicity of cyclosporin, we determined urinary excretion of 6-keto PGF1a and dinor-6-keto PGF1a (prostacyclin metabolites) and dinor-TxB2 (thromboxane metabolite) in five newly diagnosed type 1 diabetic patients during and after stopping cyclosporin therapy. In the resting state, cyclosporin had no effect on prostanoid excretion. In response to exercise, urinary excretion of 6-keto PGF1a was reduced by 50% (P less than 0.02), dinor-6-keto PGF1a by 15% (P less than 0.05) and dinor-TxB2 by 45% (P less than 0.02), while albumin excretion increased 4.5-fold (P less than 0.05) during cyclosporin therapy. Simultaneously, there was a rise in serum creatinine concentration, and renal biopsy specimens obtained from three patients showed periglomerular and interstitial fibrosis and tubular atrophy. After the discontinuation of cyclosporin therapy, serum creatinine concentrations returned to normal, histological changes improved and there was an associated rise in urinary prostanoid excretion. These data suggest that a reduction in renal prostanoid synthesis by cyclosporin may diminish renal blood flow and function, and lead to histological changes in the kidney.

Effects of ischemia/reperfusion on brain tissue prostanoids and leukotrienes in newborn pigs

We investigated the hypothesis that cerebral prostanoid and peptidoleukotriene (LTs) (LTC 4/D 4/E 4/F 4) synthesis are increased during postischemic reperfusion of newborn pig brains. Prostanoids and LTs extracted from brain tissue were determined by RIA in sham-control piglets and at, 1h, 3h, or 12h after a 20-min period of total cerebral ischemia. During reperfusion following ischemia, all regional brain tissue (cerebrum, brain stem and cerebellum) prostanoids (6- keto-PGF 1α, TXB 2, PGE 2 and PGF 2 α ) were increased at 1h compared with those in sham-control piglets. Only cerebral and brain stem 6- keto-PGF 1 α and cerebral TXB 2 remained elevated at 3h postischemia and all prostanoids returned to control levels by 12h postischemia. Brain tissue LTs were lower than prostanoids and were not altered 1, 3, or 12h following ischemia. These data indicate that 1) newborn pig brain tissue prostanoids are increased initially, and then returned to control levels at later stages of reperfusion followign ischemia; 2) LTs are present in newborn pig brain tissue, but are not increased by ischemia/reperfusion injury and therefore probably do not play a significant role in cerebral ischemia-reperfusion injury.

Calicum channel blockers and prostaglandin generation by gastric surface epithelial cells

We investigated the effects of calcium channel blockers on generation of prostaglandin (PG) E 2 and 6-keto PGF 1α by gastric mucosal surface epithelium. Surface epithelial cells (SEC) isolated from rat gastric mucosa were incubated with either verapamil (1 or 10 μg/ml), diltiazem (2.5 or 25 μg/ml) or nifedipine (2.5 or 25 μg/ml) for 30 min at 37°C in calcium containing or calcium-free medium. Verapamil (both doses)_significantly incerased PGE 2 and 6-keto PGF 1α generation by the surface epithelial cells but only in calcium containing medium. Diltiazem did not affect PG gneration in calcium containing nor calcium-free medium. Nifedipine 25 μg/ml decreased PGE 2 but increased 6-keto PGF 1α generation. The inhibitory effect of nifedipine on GPE 2 generation was abolished in calcium-free medium, while the calmodulin antagonist did not affect verapamil-induced increase in PG generation.

Canine parainfluenza type 2 and Bordetella bronchiseptica infection produces increased bronchoalveolar lavage thromboxane concentrations in beagle puppies

Acute infections in beagle puppies with canine parainfluenza virus type 2 (CPI2), and CPI2 in combination with Bordetella bronchiseptica (Bb) produce bronchiolitis and increased airways responsiveness to aerosolized histamine during the acute infection. In order to determine whether these observations were associated with increased levels of eicosanoids, the stable metabolites of thromboxane A 2 and prostacylin, thromboxane B 2 (TXB 2) and 6-keto-prostaglandin F 1α (6-keto-PGF 1α) respectively, and leukotriene B 4 were measured in the bronchoalveolar lavage (BAL) fluid of 25 beagle puppies (age = 76 ± 1 days, mean ± SEM) 3–4 days after no infection (control, n = 6), inoculation with both CPI2 and Bb (CPI2-Bb, n = 11), inoculation with CPI2 alone (CPI2, n = 4), and inoculation with Bb alone (Bb, n = 4). In addition, plasma levels of TXB 2 and 6-keto-PGF 1α were measured before and after infection in the CPI2-Bb and control groups. The BAL concentration of thromboxane B 2 was increased in the CPI2-Bb group (520 ± 120 pg/ml), but not in the CPI2 (88 ± 40 pg/ml), Bb (235 ± 100 pg/ml), or control groups (120 ± 60 pg/ml, p < 0.01). There also was a borderline increase in BAL concentration of LTB 4 in the CP12-Bb group. No differences were observed in the BAL concentration of 6-keto PGF 1α. Furthermore, neither TXB 2 nor PGF 1α was elevated in the plasma of control or CPI2-Bb puppies. These data suggest that increased thromboxane concentrations in BAL fluid are associated with histamine hyperresponsiveness during acute infection in the CPI2-Bb group.

Tumor necrosis factor production by murine resident peritoneal macrophages is enhanced by dietary n−3 polyunsaturated fatty acids

Tumor necrosis factor (TNF) is a macrophage derived peptide that has an antitumor action and modulates immune and inflammatory reactions. Dietary fatty acids may modulate TNF production as dietary n−3 polyunsaturated fatty acids suppress human monocyte TNF production, but enhance its secretion by murine peritoneal macrophages. Mice were maintained for 5 weeks on diets containing different amounts of n−3 and n−4 fatty acids. TNF, PGE 2 and 6-keto PGF 1α production was monitored following in vitro stimulation of resident peritoneal macrophages with lipopolysaccharide. Macrophages from mice fed the high n−3 diet produced 8-fold more TNF and half the PGE 2 produced by macrophages from mice on the other diets. Indomethacin caused an increase in the TNF production by macrophages from mice on all diets but macrophages from mice on the high n−3 diet produced more TNF than macrophages from mice on the other diets. Exogenous PGE 2 (100 nM) greatly decreased TNF production by macrophages from mice on all diets, but macrophages from mice on the high n−3 diet secreted 70% more TNF than macrophages from mice fed the other diets, indicating that PGE 2 is only partly responsible for the effects observed. The results show that feeding n−3 polyunsaturated fatty acids may cause enhanced TNF production by resident peritoneal macrophages and that PGE 2 is partly responsible for the effect.

Effects of ozone on lung mechanics and cyclooxygenase metabolites in dogs

To determine if acute exposure to ozone can cause changes in the production of cyclooxygenase metabolites of arachidonic acid (AA) in the lung which are associated with changes in lung mechanics, we exposed mongrel dogs to 0.5 ppm ozone for two hours. We measured pulmonary resistance (R 1) and dynamic compliance (C dyn) and obtained methacholine dose response curves and bronchoalveolar lavagate (BAL) before and after the exposures. We calculated the provocative dose of methacholine necessary to increase R L 50% (PD 50) and analyzed the BAL for four cyclooxygenase metabolites of AA: a stable hydrolysis product of prostacyclin, 6-keto-prostaglandin F 1α (6-keto-PgF 1α); prostaglandin E 2 (PgE 2); a stable hydrolysis product of thromboxane A 2, thromboxane B 2 (TxB 2); and prostaglandin F 2α (PgF 2α). Following ozone exposure, R L increased from 4.75 +/- 1.06 to 6.08 +/- 1.3 cmH 2O/L/sec (SEM) (p < 0.05), C dyn decraesed from 0.0348 +/- 0.0109 to .0217 +/- .0101 L/cmH 2O (p < 0.05), and PD 50 decreased from 4.32 +/- 2.41 to 0.81 +/- 0.49 mg/cc (p<0.05). The baseline metabolite levels were as follows: 6-keto PgF 1α: 96.1 +/- 28.8 pg/ml; PgE 2: 395.8 +/- 67.1 pg/ml; TxB 2: 48.5 +/- 11.1 pg/ml; PgF 2α: 101.5 +/- 22.6 pg/ml. Ozone had no effect on any of these prostanoids. These studies quantify the magnitude of cyclooxygenase products of AA metabolism in BAL from dog lungs and demonstrate that changes in their levels are not prerequisites for ozone-induced changes in lung mechanics or airway reactivity.

Expression of prostaglandin [formula omitted] synthase (cyclooxygenase) during murine fetal thymic development

Fetal thymic lobes in organ culture have been shown to have the capacity to metabolize [ 14C]arachidonic acid (AA) to prostaglandins (PGs), including 6-ketoPGF 1α, PGF 2α, PGE 2, and PGA 2. Inhibition of AA metabolism results in inhibition of growth and Thy 1 expression during thymic organ culture. We report herein that freshly-isolated fetal thymic lobes also have the capacity to metabolize [ 14C]AA to PGs and HETEs at Days 14 and 16 of prenatal murine development. RNA encoding phospholipase A 2, which liberates arachidonic acid from membrane phospholipids, and Cyclooxygenase (prostaglandin G H synthase), the first enzyme involved in the conversion of AA to PGs, are expressed during thymic development. We have localized the cyclooxygenase protein to stromal cells in the fetal and adult thymus. Exogenous AA or an analogue of PGI 2 (iloprost) stimulated growth of fetal thymocytes in organ culture. These findings, together with our studies of the morphology of thymic lobes cultured with inhibitors of arachidonate metabolism, support the hypothesis that PGs are required for thymocyte proliferation during thymic development.

Hypoxia-induced change in prostanoids production and coronary flow in isolated rat heart

The contribution of prostanoids to the change in coronary flow induced by hypoxia was examined in Langendorff-perfused rat heart. In the coronary effluent, 5 prostanoids, i.e., prostaglandins (PGs) D 2, E 2, and F 2 α , 6-keto PGF 1α and thromboxane (TX) B 2, were quantified by GC/MS, whereas PGA 2 , B 2 and E 1 were not detected under any conditions. During hypoxia, coronary flow initially increased to 189.5 ± 17.8% of the control, and at the same time release of all PGs, except for TXB 2 , increased significantly (6-keto PGF 1α : from 3.57 ± 0.98 to 5.54 ± 1.25 pmol/min·g, D 2: from 1.47 ± 0.26 to 2.22 ± 0.26 pmol/min·g, E 2: from 0.27 ± 0.08 to 0.96 ± 0.21 pmol/min·g, F 2 α : from 0.23 ± 0.09 to 0.48 ± 0.13 pmol/min·g, TXB 2 : from 0.61 ± 0.10 to 0.58 ± 0.15 pmol/min·g). During the later phase (10–20 min) of hypoxia, coronary 1 2 ow decreased without concomitant decrease in the release of PGs. The administration of indomethacin (10 μ m) and aspirin (1 m m) did not affect the normoxic coronary flow. However, during the early phase of hypoxia, they significantly suppressed the increase in coronary flow. Administration of arachidonic acid (1 mg/l) increased PG release 6.4–12.5-fold and increased coronary flow to 176.1 ± 6.5% of the control level. In the presence of arachidonic acid, there was a good correlation between the coronary flow and the amount of released vasodilative PGs ( PGE 2 and 6-keto PGF 1α ), suggesting the contribution of these PGs to coronary vasoregulation. On the other hand, when hearts were made hypoxic in the presence of arachidonic acid, percentage increase in PG release was much reduced, and similarly, coronary flow was not elevated. These results indicate that the increase in coronary flow during the early phase of hypoxia is mediated, at least in part, by the increased release of vasodilative PGs.