Noradrenaline-Induced Prostaglandin Production by Sympathetic Postganglionic Neurons Is Mediated by α2-Adrenergic Receptors

In this study we have demonstrated that noradrenaline increases the levels of prostaglandin E2 and prostaglandin I2 (detected as the stable metabolite 6-keto-prostaglandin F1 alpha) synthesized by homogenates of superior cervical ganglia from the adult rat. This noradrenaline-induced prostaglandin production was further characterized: (a) Selective destruction of adrenergic sympathetic postganglionic neurons in the ganglia using 6-hydroxydopamine abolished both basal and stimulated prostaglandin production. (b) Elimination of preganglionic cholinergic sympathetic nerve terminals in the ganglia had no effect. (c) Mepacrine (a phospholipase inhibitor) and indomethacin (a cyclooxygenase inhibitor) attenuated both basal and stimulated prostaglandin production. (d) Yohimbine, but not prazosin, suppressed the noradrenaline dose-response curve for prostaglandin production. The results of these experiments show that, in vitro, noradrenaline stimulates de novo synthesis of prostaglandin E2 and prostaglandin I2 by sympathetic postganglionic neurons. This stimulation by noradrenaline appears to result from action at an alpha 2-adrenergic receptor.     

Prostaglandin production by type II alveolar epithelial cells.

Prostaglandin production was studied in fetal and adult type II alveolar epithelial cells. Two culture systems were employed, fetal rat lung organotypic cultures consisting of fetal type II cells and monolayer cultures of adult lung type II cells. Dexamethasone, thyroxine, prolactin and insulin, hormones which influence lung development, each reduced the production of prostaglandin E and F alpha by the organotypic cultures. The fetal cultures produced relatively large quantities of prostaglandin E and F alpha and smaller quantities of 6-keto-prostaglandin F1 alpha and thromboxane B2. However, prostaglandin E2 production was predominant. In contrast, the adult type II cells in monolayer culture produced predominantly prostacyclin (6-keto-prostaglandin F1 alpha) along with smaller quantities of prostaglandin E2 and F2 alpha. The type II cells were relatively unresponsive to prostaglandins. Exogenously added prostaglandin E, had no effect on cell growth, and only a minimal effect on cyclic AMP levels in the monolayer cultures.     

Differential effects of sex steroids on prostaglandin secretion by male and female cultured piglet endothelial cells

The effect of sex steroids, 17 beta-estradiol and testosterone, on the production of 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha and prostaglandin E2 was studied in cultures of piglet aorta endothelial cells. In cells isolated from female animals both steroids stimulated the secretion of prostaglandins. In contrast, sex steroids did not affect prostaglandin synthesis by endothelial cells taken from male animals. In addition, female endothelial cells convert testosterone into estriol, estrone and estradiol. Estradiol-induced stimulation of prostacyclin production may explain in part the beneficial role generally attributed to naturally occurring estrogens in cardiovascular diseases.     

The effect of acute hypoxia on prostaglandin release in perfused human fetal placenta

The release of prostaglandin E2 and F2 alpha, thromboxane B2 and 6-keto-prostaglandin F1 alpha was measured in isolated human placental cotyledons perfused under high- and low-oxygen conditions. Also the effect of reoxygenation on prostaglandin production was studied. During the high-oxygen period, prostaglandin E2 accounted for 44% and 6-keto-prostaglandin F1 alpha for 28% of all prostaglandin release, and the rank order of prostaglandin release was E2 greater than 6-keto-prostaglandin F1 alpha greater than thromboxane B2 greater than prostaglandin F2 alpha. Hypoxia had no significant effect on quantitative prostaglandin release, but the ratio of prostaglandin E2 to prostaglandin F2 alpha was significantly increased. After the hypoxic period during reoxygenation the release of 6-keto-prostaglandin F1 alpha was significantly decreased, as was the ratio of 6-keto-prostaglandin F1 alpha to thromboxane B2. Also the ratio of the vasodilating prostaglandins (E2, 6-keto-prostaglandin F1 alpha) to the vasoconstricting prostaglandins (thromboxane B2, prostaglandin F2 alpha) was decreased during reoxygenation period. With the constant flow rate, the perfusion pressure increased during hypoxia in six and was unchanged in three preparations. The results indicate that changes in the tissue oxygenation in the placenta affect prostaglandin release in the fetal placental circulation. This may also have circulatory consequences.     

交感传出在大鼠糖尿病性痛过敏中的作用

交感传出和前列腺素（ＰＧｓ）在周围神经不全损伤和炎症所引起的痛过敏中起重要作用,它们对糖尿病性痛过敏影响尚不清楚。本工作先给大鼠腹腔注射６－羟多巴胺（６－ＯＨＤＡ）损毁交感节后神经元（ＳＰＧＮｓ）末梢后,再给予链脲佐菌素（ＳＴＺ）以建立６－ＯＨＤＡ糖尿病大鼠模型,在连续４周的观察中这组大鼠伤害性爪回缩阈值（ＮＰＷＴ）和甩尾反向潜伏期（ＴＥＬ）没有明显变化,而糖尿 病组大鼠的痛阈显著降低,并伴有痛过     

Arachidonic acid metabolism and prostaglandin production by primate preimplantation blastocysts.

Preimplantation embryos of many species are known to synthesize prostaglandins. These tissue hormones are believed to influence embryonic metabolism, as well as embryo-maternal interaction during implantation although their putative role(s) remains obscure. Here, prostaglandin production by blastocysts from cynomolgus monkeys (Macaca fascicularis) was examined qualitatively during in vitro culture. Tritium labelled arachidonic acid was metabolized to 6 keto-prostaglandin F1 alpha, 2,3-dinor-prostaglandin F1 alpha and thromboxane B2, as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha, and thromboxane B2 as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha and thromboxane B2 were identified by specific RIA's. Our data suggest that the main arachidonic acid metabolites produced by blastocysts of cynomolgus monkeys are prostacyclin and thromboxane.     

Distribution of prostaglandin biosynthetic pathways in organs and tissues of the fetal lamb

Five prostaglandins, i.e. prostaglandins E2, F2alpha and D2, 6-keto-prostaglandin F1alpha and thromboxane B2, were measured by mass spectrometry. Homogenates of fetal lamb brain, lung, liver, spleen and kidney and the ductus arteriosus, aorta and pulmonary artery formed different amounts of each product. Although the main prostaglandin in the fetal organs was prostaglandin E2, arterial tissue formed mostly 6-keto-prostaglandin F1alpha. These results demonstrate significant differences between organs and tissues in the relative direction of the 'prostaglandin synthetase' enzyme complex.     

Prostaglandin hyperalgesia, IV: a metabolic process

Prostaglandin E2, prostacyclin and Db-cAMP injected into the rat paw induce hyperalgesia. This hyperalgesic effect of the prostaglandins but not of Db-CAMP was blocked by pre-treatment of the animals with cycloheximide. Prostaglandin hyperalgesia thus seems to be dependent on the triggering of some metabolic process which enhances the effects of physical or chemical stimuli.     

Central venous concentrations of immunoreactive prostaglandins E,F, and 6-keto-prostaglandin F1 in eclampsia.

Concentrations of prostaglandins E, F, and 6-keto-prostaglandin F1 alpha were estimated in central venous blood and amniotic fluid in 21 women with eclampsia and 16 healthy pregnant controls. Central venous blood concentrations of 6-keto-prostaglandin F1 alpha and prostaglandin E were significantly lower in patients than controls before delivery and remained reduced for at least 48 hours after delivery. Low concentrations of prostaglandins E and 6-keto-prostaglandin F1 alpha are probably directly related to the pathogenesis of eclampsia.     

Altered glomerular eicosanoid biosynthesis in uranyl nitrate-induced acute renal failure

The present studies were designed (1) to examine the pattern of changes in eicosanoid biosynthesis in isolated rat glomeruli, and (2) to correlate these changes with the previously observed alterations in renal perfusion and glomerular filtration rate which occur after uranyl nitrate administration, a model of toxin-induced acute renal failure. In the first part of this study, the in vitro and the in vivo effects of two cyclooxygenase inhibitors were examined for their ability to inhibit rat glomerular eicosanoid biosynthesis. Inhibition of prostaglandin E2 and prostaglandin F2 alpha generation by 1 mM aspirin in vitro was 76 and 82%, respectively. Similar inhibitions of 85 and 72% of biosynthesis of the above-mentioned lipids by 0.1 mM indomethacin were also noted. Intraperitoneal administration of aspirin (150 mg/kg) resulted in a significant inhibition of 88% or greater of prostaglandin E2, prostaglandin F2 alpha, 6-keto-prostaglandin F2 alpha, and thromboxane B2 biosynthesis. These results indicated that the expected alterations produced under in vivo conditions were detectable by in vitro techniques used in this study. 24 h after the administration of uranyl nitrate (25 mg/kg), significant increases in the biosynthesis of prostaglandin E2 (124%) and prostaglandin F2 alpha (88%) were observed when compared to the control values. No significant changes in prostacyclin or thromboxane formation were noted at this time. A further increase in the biosynthesis of prostaglandin E2 (248%), prostaglandin F2 alpha (262%), and a significant increase in prostacyclin (120%), measured as 6-keto-prostaglandin F1 alpha, were noted at 48 h. No changes in thromboxane B2 biosynthesis were noted. It is concluded that these data are consistent with the hypothesis that the increased glomerular biosynthesis of vasodilator eicosanoids (i.e., prostaglandin E2 and prostacyclin) may play a significant role in the homeostatic regulation of renal perfusion and glomerular filtration after acute toxic injury to the kidney.     

Induction of prostacyclin formation by sodium n-butyrate in a cloned epithelial liver cell line

The effect of sodium n-butyrate on prostaglandin synthesis in cultured cells was examined. Exposure of BC-90 cells, a clone of an epithelial rat liver cell line, to 1 mM sodium n-butyrate for 40 h induced prostacyclin production. Prostacyclin synthesis was proved by demonstrating: (1) production of labeled 6-ketoprostaglandin F1 alpha by treating [14C]arachidonic acid pre-labeled cells with calcium ionophore A23187, (2) production of unstable substance that inhibited adenosine diphosphate-induced platelet aggregation, and (3) conversion of [14C]arachidonic acid to 6-ketoprostaglandin F1 alpha in homogenates of n-butyrate-treated cells. Untreated control cells showed negligible prostaglandin synthesis. Untreated cell homogenates did not convert [14C]arachidonic acid to any prostaglandins, but they converted [14C]prostaglandin H2 to prostacyclin. Induction of prostacyclin production by n-butyrate was also demonstrated with cells that had been treated with acetylsalicylic acid before n-butyrate treatment in acetylsalicylic acid-free medium. Incorporation of [3H]acetylsalicylic acid by sodium n-butyrate-treated cells increased in accordance with treatment time, while that of untreated cells did not change during culture. There was no difference in the phospholipase A2 activities of n-butyrate-treated and -untreated cells. From these findings, the possibility that n-butyrate induced prostacyclin in BC-90 cells through induction of fatty acid cyclooxygenase activity is discussed.     

Prostacyclin and prostaglandin synthesis in isolated brain capillaries

The synthesis of prostacyclin and prostaglandins was examined in isolated blood-free brain capillaries of guinea-pigs and rats using 1-14C-arachidonic acid as a precursor. The main prostaglandins synthesized by guinea-pig microvessels were prostaglandin D2 and prostaglandin E2. Substantially less prostaglandin F2 alpha or the prostacyclin stable metabolite, 6-oxo-prostaglandin F1 alpha was synthesized. Rat capillary prostaglandin distribution differed substantially from that of the guinea-pigs although the principle prostaglandin was also PGD2. Total prostaglandin conversion was greater in guinea-pig capillaries than in the rat. Norepinephrine stimulated the prostaglandin forming capacity of blood free cerebral microvasculature of guinea-pigs. Prostacyclin and prostaglandins could be involved in the activity dependent regulation of regional cerebral blood flow and permeability.     

On the metabolism of prostaglandins by human gastric fundus mucosa.

1.Specific radioimmunoassays for the prostaglandins E2, F2alpha and A2 and the metabolites 13,14-dihydro-15-keto-prostaglandin E2, 15-keto-prostaglandin F2alpha and 13,14-dihydro-15-keto-prostaglandin F2alpha were used to study the metabolism of prostaglandins by gastroscopically obtained small biopsy specimens of human gastric fundus mucosa. 2.Three prostaglandin-metabolizing enzymes were found in the 100 000 X g supernatant of human gastric fundus mucosa, 15-hydroxy-prostaglandin-dehydrogenase, delta13-reductase and delta9-reductase. The specific activity was highest for 15-hydroxy-prostaglandin-dehydrogenase and lowest for delta9-reductase. 3.Formation of prostaglandin A2 (or B2) was not observed under the same conditions. 4.None of the three enzyme activities detected in the 100 000 X g supernatant was found in the 10 000 X g and 100 000 X g pellets of human gastric fundus mucosa. 5.The results indicate that high speed supernatant derived from human gastric mucosa can rapidly metabolize prostaglandin E2 and prostaglandin F2alpha to the 15-keto and 13,14-dihydro-15-keto-derivatives. Furthermore, prostaglandin E2 can be converted to prostaglandin F2alpha, the biological activity of which, on gastric functions, differs from that of prostaglandin E2.     

Effects of isolation and culture on prostaglandin synthesis by porcine aortic endothelial and smooth muscle cells

Freshly isolated neonatal porcine aortic tissue (smooth muscle with or without endothelium present) produced approximately 30 ng/mg wet tissue of 6-oxo-prostaglandin F1 alpha (the stable hydrolysis product from prostacyclin) and approximately 15 ng/mg of prostaglandin E2, as measured by radioimmunoassay after 24 h incubation in culture medium. Primary cultures of porcine endothelial and smooth muscle cells (isolated by enzymic digestion of aortic tissue) exhibited the same pattern of prostaglandin production, but absolute values were greater than for fresh tissue, particularly in the case of endothelium. Subcultures of endothelium produced smaller amounts of prostaglandins, although the pattern remained similar. In contrast, subcultures of smooth muscle cells produced a greater total amount of prostaglandins than did primary cultures, and the main product was prostaglandin E2. Experiments with [14C] prostaglandin H2 or [14C]arachidonic acid confirmed that aortic tissue, cultured endothelium, and primary cultures or aortic smooth muscle cells synthesized prostacyclin, and demonstrated that subcultured smooth muscle cells enzymically isomerised prostaglandin H2 to prostaglandin E2. Kinetic studies showed that prostaglandin production by cultured vascular cells was transiently increased by subculture or changing the growth medium, and that production per cell declined with increasing cell density. The change in pattern of prostaglandin production during culture was shown to be due to a rapid decline in the rate of prostacyclin production (which apparently began immediately after tissue isolation), together with a more gradual rise in prostaglandin E2 production. These results indicate that the amounts and ratios of prostaglandins produced by vascular endothelial and smooth muscle cells are greatly affected by the conditions used to isolate and culture the cells; vascular cells in vivo may similarly alter their pattern of prostaglandin production in response to local changes in their environment.     

Effect of in vitro aging on 6-ketoprostaglandin F1 alpha-producing activity in cultured human diploid lung fibroblasts.

Prostaglandin synthesis in human diploid fibroblasts was studied by incubating [14C]-arachidonic acid with cell homogenates. The majority of prostaglandins produced in young cells was 6-ketoprostaglandin F1 alpha. The 6-ketoprostaglandin F1 alpha-producing activity of cultures declined with in vitro aging, and was almost undetectable at the senescent stage, while total production of thromboxane B2, prostaglandin F2 alpha and prostaglandin E2-like metabolites increased with in vitro aging.     

Radioimmunologic identification of prostaglandins produced by serum-stimulated mouse embryo palate mesenchyme cells

High-performance liquid chromatography and radioimmunoassay were used to identify the prostaglandins synthesized by mouse embryo palate mesenchyme cells. Serum stimulated the release of several different metabolites of arachidonic acid including 6-ketoprostaglandin F1 alpha (the stable product of prostacyclin, prostaglandin I2), prostaglandin E2 and prostaglandin F2 alpha. Compared to control cells, the serum-stimulated cells produce elevated levels of prostaglandin E2 (36-fold), 6-ketoprostaglandin F1 alpha (15-fold) and prostaglandin F2 alpha (7-fold). The acetylenic analogue of arachidonic acid, 5,8,11,14-eicosatetraynoic acid prevented this accelerated synthesis.     

The hyperalgesic effects of prostacyclin and prostaglandin E2.

Hyperalgesia induced in rat paws or dog knee joints by prostacyclin (PGI2) and prostaglandin E2 was measured by a modification of the Randall-Selitto method (1) or by the degree of incapacitation (2). In both species PGI2 induced an immediate hyperalgesic effect but the effect of PGE2 had a longer latency. Low doses of PGI2 caused a short lasting effect but PGE2, large doses of PGI2 or successive administration of small doses of PGI2 caused a long lasting effect. It is suggested that prostacyclin mediates rat paw hyperalgesia induced by carrageenin. The long lasting hyperalgesic effect of PGE2 and high doses of PGI2 is possibly an indirect effect caused by stimulation of a sensory nerve sensitising mechanism.     

Calcitonin enhances production of prostaglandins by stimulated human monocytes

Stimulated monocytes produce prostaglandins that may play a role in bone resorption. We studied the effects of salmon calcitonin (sCT) on human monocyte production of various prostaglandin metabolites. Latex particle-stimulated human monocyte production of prostaglandin E2, thromboxane A2 measured as thromboxane B2, and prostacyclin measured as 6-keto-PGF1 alpha was each increased in the presence of sCT. This effect required surface stimulation, was blocked by indomethacin, was less marked with equivalent concentrations of human calcitonin, and was not seen with parathyroid hormone. Calcitonin specifically affects prostaglandin pathways in stimulated human monocytes.     

Prostanoid synthesis in peripheral nerve

The transformation of [1-14C]arachidonic acid into radiolabeled prostanoids was studied with homogenates and desheathed sciatic nerves of rats and frogs. All of the preparations studied were shown to synthesize prostaglandins; the specific prostanoids made were characterized by their migration on thin-layer chromatograms in three separate solvent systems. Both desheathed rat nerve and homogenates synthesize prostaglandin E2, prostaglandin F2 alpha, prostaglandin D2, 6-ketoprostaglandin F1 alpha and thromboxane B2. With preparations from frog nerve, prostaglandin E2 was the major prostanoid product formed. Several conditions were able to modulate the production of prostaglandin E2 with desheathed frog nerve. Electrical stimulation at high frequency (100 Hz) for 30 min increased the formation of labeled prostaglandin E2. Inclusion of glutathione also affected prostaglandin E2 formation. A lower concentration (0.1 mM) stimulated prostaglandin synthesis, while 1 mM glutathione was partially inhibitory. In both the rat and frog system, prostanoid synthesis was suppressed by indomethacin and aspirin.     

Prostaglandin synthesis and catabolism in the gastric mucosa: studies in normal rabbits and rabbits immunized with prostaglandin E2

Antral and fundic mucosal homogenates obtained from prostaglandin E2-immunized rabbits converted 14C-arachidonic acid to prostaglandin E2, 6-keto prostaglandin F1 alpha, prostaglandin F2 alpha, and prostaglandin D2. Percentage conversion of 14C-arachidonic acid to these prostaglandin products was not significantly different in prostaglandin E2-immunized rabbits compared with control rabbits (thyroglobulin-immunized and unimmunized rabbits combined). Synthesis of 6-keto prostaglandin F1 alpha, prostaglandin E2 and 13,14-dihydro 15-keto prostaglandin E2 from endogenous arachidonic acid after vortex mixing fundic mucosal homogenates was similar in prostaglandin E2 immunized rabbits and control rabbits. Both in prostaglandin E2-immunized rabbits and controls, 3H-prostaglandin E2 was catabolized extensively by the fundic mucosa, whereas 3H-6-keto prostaglandin F1 alpha, 3H-prostaglandin F2 alpha, and 3H-prostaglandin D2 were not catabolized to any appreciable extent. The rate of catabolism of PGs was not significantly different in prostaglandin E2-immunized rabbits and control rabbits, with the exception of prostaglandin F2 alpha which was catabolized slightly more rapidly in prostaglandin E2-immunized rabbits. These results indicate that development of gastric ulcers in prostaglandin E2-immunized rabbits is not associated with an alteration in the capacity of the gastric mucosa to synthesize or catabolize prostaglandins.