Chemical synthesis of tritium-labeled prostaglandins A, B and F

Formation of prostaglandins A, B and F from prostaglandin E has been studied. Synthesis of tritium-labelled prostaglandins A1, A2, B1, B2, F1 alpha, F2 alpha, F1 beta, F2 beta of high molar radioactivity from highly labelled PGE1 and PGE2 is described.     

PGE1 not PGF2 alpha reverses the anti-actin antibody stimulation of protein phosphorylation and DNA synthesis in L cells

The effects of prostaglandins E1 and F2 alpha upon the anti-actin antibody-induced stimulation of DNA synthesis and protein phosphorylation were studied in L cells. This system was previously shown by us to exhibit a rapid turnover of arachidonic acid in phospholipids which was inhibited by non-toxic concentrations of indomethacin, suggesting participation of cyclooxygenase-derived prostaglandins (Lipids 19:239, 1984). Prostaglandin E1 in a dose dependent manner selectively inhibited both protein phosphorylation and DNA synthesis in anti-actin antibody-stimulated cells. Prostaglandin F2 alpha was without effect. Indomethacin also produced a dose related inhibition of the antibody stimulation of protein phosphorylation and DNA synthesis. We conclude that prostaglandins, possibly derived from liberated arachidonic acid, play an important regulatory role in the stimulatory signal conveyed to L cells by perturbing antibody ligands.     

Metabolism of prostaglandins, prostaglandin analogs and thromboxane B2 by lung and liver microsomes from pregnant rabbits

Liver microsomes from pregnant rabbits converted prostaglandins F2 alpha, E1, and E2 to their 20-hydroxy metabolites along with smaller amounts of the corresponding 19-hydroxy compounds. Prostaglandins E1 and E2 were also reduced to prostaglandins F1 alpha and F2 alpha, respectively, and prostaglandin E1 was isomerized to 8-isoprostaglandin E1. The above products were also identified after incubation of prostaglandins with liver microsomes from non-pregnant rabbits. In this case, the yield of 20-hydroxy metabolites was much lower. Thromboxane B2 and a number of prostaglandin F2 alpha analogs were also hydroxylated by lung and liver microsomes from pregnant rabbits. The relative rates of hydroxylation by lung microsomes were: prostaglandin E2 approximately prostaglandin F2 alpha approximately 16,16-dimethylprostaglandin F2 alpha approximately 13,14-didehydroprostaglandin F2 alpha greater than thromboxane B2 greater than 15-methylprostaglandin F2 alpha approximately 17-phenyl-18,19,-20-trinorprostaglandin F2 alpha approximately ent-13,14-didehydro-15-epiprostaglandin F2 alpha. Similar results were obtained with liver microsomes except that thromboxane B2 was a relatively poorer substrate for hydroxylation.     

Effect of prostaglandins on protein, RNA, DNA and collagen synthesis in experimental wounds.

The effect of exogenous prostaglandins E1, E2 and F2alpha (PGE1, PGE2 and PGF2alpha) on 3H-leucine, 3H-uridine, 3H-thymidine and 3H-proline incorporation in experimental cutaneous wounds has been studied in rats. Prostaglandins E1 and E2 markedly stimulate the incorporation of these tritiated precursors, into protein, RNA, DNA and collagen synthesis, whereas F2 inhibits it. All tested prostaglandins exhibit their maximum effect within the first hours following administration. Most active is PGE1. These observations indicate that application of prostaglandins significantly stimulate incorporation with protein, RNA, DNA and collagen synthesis in the skin of wounded rats and thus, may play a role in epidermal cell growth and division as well as in scar-forming tissue.     

Effect of prostaglandins A1, A2, B1, B2, E2 and F2 alpha on human umbilical cord vessels

Human umbilical blood vessels have the ability to close spontaneously following delivery at term. It has been suggested that prostaglandins may have a possible physiological role in its closure. This study investigates the effects of 6 naturally occurring prostaglandins (A1, A2, B1, B2, E2, F2a) on the umbilical blood vessels. Umbilical cords were collected from cases of normal spontaneous vaginal deliveries and cesarian section at term. A total of 41 strips of umbilical arteries and 26 strips of umbilical veins from 24 cords were used. A 4-point bioassay method was used to compare the potency of prostaglandins A1, A2, B1 and F2a with PGE2. The effect of Polyphloretin Phosphate (PPP) on prostaglandin-induced contractions was studied on umbilical artery strips from 12 cords. The 6 prostaglandins exerted a stimulant effect on the isolated strips of human umbilical arteries. Prostaglandin B2 was the most potent compound on the umbilical vein, followed by PGA2. PPP in the concentration range of 10 to 40 mcg/ml completely eliminated the responses of PGE2, F2a, A1, A2, and B1. Responses to PGB2 were considerably but not completely abolished. PPP (up to 40 mcg/ml) did not affect contractions induced by 5-hydroxytryptamine, suggesting the presence of discrete receptor sites in the blood vessels for different pharmacologically active compounds. This is the first report of the constrictor effect of PGA and PGB compounds. These naturally occuring prostaglandins with high potencies (compared with other prostaglandins and other vasoactive substances) may play a role in spontaneous closure of umbilical vessels. PGE1, E2, F1 and F2a are found in umbilical blood vessels obtained at term.     

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.     

Area postrema: cholinergic and noradrenergic regulation of emesis. A new concept

In unanaesthetized cats the biochemical mechanisms and the functional characteristics of the emetic action of injection of noradrenaline and McN-A-343, a ganglionic muscarinic stimulant into the cerebral ventricle (i.c.v.) through chronically implanted cannulae were investigated. Both produced dose-dependent and shortlasting emetic response. The emesis evoked by noradrenaline was abolished, whereas the emesis induced by McN-A-343 was not completely blocked after ablation of the area postrema. Further, the emetic response to noradrenaline as well as to McN-A-343 was attenuated or blocked in cats pretreated with 6-hydroxydopamine (i.c.v.) and hemicholinium (i.c.v.); it was abolished in cats pretreated with reserpine (i.c.v.). On the other hand, the emetic response to i.c.v. noradrenaline and to i.c.v. McN-A-343 was not virtually altered in cats pretreated with bretylium (i.c.v.), alpha-methyl-p-tyrosine (i.c.v.) and 5,6-dihydroxytryptamine (i.c.v.). It is postulated that noradrenergic neurones as well as cholinergic axon terminals within the area postrema are necessary for the emetic action of noradrenaline, whereas cholinergic axon terminals within the area postrema subserve the emetic response to McN-A-343. A functional link between cholinergic terminals and noradrenergic neurones as well as a modulatory role of noradrenergic afferents on cholinergic afferents mediating emesis within the area postrema is further proposed. Thus, noradrenergic neurones might represent a common site of confluence of different inputs subserving the emesis in the area postrema. Finally, cholinergic terminals sometimes bypass this area and synapse in the emetic regions of the brainstem regulating emesis.     

Uterine vein prostaglandin levels in late pregnant dogs.

We studied the uterine venous plasma concentrations of prostaglandins E2, F2 alpha, 15 keto 13,14 dihydro E2 and 15 keto 13,14 dihydro F2 alpha in late pregnant dogs in order to evaluate the rates of production and metabolism of prostaglandin E2 and F2 alpha in pregnancy in vivo. We used a very specific and sensitive gas chromatography-mass spectrometry assay to measure these prostaglandins. The uterine venous concentrations of prostaglandin E2 and 15 keto 13,14 dihydro E2 were 1.35 +/- .27 ng/ml and 1.89 +/- .37 ng/ml, respectively; however, we could not find any prostaglandin F2 alpha and very little of its plasma metabolite in uterine venous plasma. Since uterine microsomes can generate prostaglandin F2 alpha and E2 from endoperoxides, prostaglandin F2 alpha production in vivo must be regulated through an enzymatic step after endoperoxide formation. Prostaglandin E2 is produced by pregnant canine uterus in quantities high enough to have a biological effect in late pregnancy; however, prostaglandin F2 alpha does not appear to play a role at this stage of pregnancy.     

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.     

Human neutrophils transform prostaglandins by a myeloperoxidase-dependent mechanism

Intact human neutrophils, incubated with the soluble stimulant phorbol myristate acetate, discharge lysosomal components, generate oxygen metabolites, and transform exogenous 6-keto-prostaglandin F1 alpha, prostaglandin E2, and prostaglandin F2 alpha as assessed by thin layer radiochromatography. Neutrophils alone were incapable of transforming the prostaglandins. The addition of catalase or the myeloperoxidase inhibitor, azide, protected all three prostaglandins from the phorbol-stimulated neutrophils. Neither superoxide dismutase, heat-inactivated catalase, nor albumin had any inhibitory effect in this system. A model system consisting of glucose-glucose oxidase, as a source of H2O2, purified myeloperoxidase, and chloride was also able to transform the prostaglandins in an identical fashion. Neither glucose-glucose oxidase alone nor glucose-glucose oxidase and myeloperoxidase under chloride-free conditions were able to mediate this transformation. Thus, it appears that intact human neutrophils can transform prostaglandins by a mechanism dependent on H2O2, the lysosomal enzyme myeloperoxidase, and chloride. Given the importance of prostaglandins in regulating immune function, neutrophil-dependent prostaglandin transformation could play a novel role in modulating the inflammatory response.     

The prostaglandin and cyclic nucleotide levels in the organs of mice with experimental anthrax intoxication]

In this work the influence of Bacillus anthracis toxin, introduced intraperitoneally in a dose of LD100, on the content of prostaglandins E and F2 alpha, 6-ketoprostaglandin F1 alpha, thromboxane, cAMP and cGMP in the lungs, heart, liver and spleen of BALB/c mice in the time course of experimental intoxication has been studied. The concentration and proportion of prostaglandins and cyclic nucleotides have been shown to undergo-sharp changes in all organs under study in the process of intoxication. The level and proportion of prostaglandins in the lungs ensures the development of vaso- and bronchodilatation processes even at early stages of the action of the toxin. B. anthracis toxin sharply increases the content of cGMP in the organs under study and cAMP in the liver. The activating effect on the adenylate cyclase system of tissue cells is not linked with the action of the edematous factor of the toxin. The role of cyclic nucleotides and prostaglandins in the development of pulmonary edema in intoxication with B. anthracis toxin is discussed.     

Characteristics of prostaglandin E1 interaction with components of biological membranes

To estimate the connection between physico-chemical characteristics and biological activity of prostaglandins the interaction of prostaglandin E1 with biological membrane lipids was studied. It is shown that as a result of prostaglandin interaction with phosphatidylcholine a complex is formed that behaves as an individual component and occupies in the surface layer twice as large area than the complex with prostaglandin F2 alpha. The prostaglandin E1 film collapses earlier than F2 alpha. Both facts indicate that the first is more friable. A difference in morphology of prostaglandin monolayers was revealed by electron microscopy. When studying the catalytic activity of peroxidase incorporated in prostaglandin E1 and F2 alpha monolayers some differences were also revealed. In the second case oxidation with methylblue located under the monolayer proceeds more actively. The results obtained point to the connection between the regulatory function of prostaglandins and their chemical structure. Molecular rearrangements of the monolayer caused by prostaglandin incorporation were recorded.     

Basal level of human platelet prostaglandins: PGE1 is more elevated than PGE2.

Radioimmunoassays of platelet prostaglandins E1 and F1 alpha in platelet rich plasma or platelet suspension, demonstrate that both PGE1 and PGF1 alpha are present at higher concentrations than prostaglandins E2 and F2 alpha. Gas chromatography--mass spectrometry determinations of prostaglandins E1 and E2 in resting washed platelets confirm this difference. Lastly, there is a greater incorporation of [1--14C] acetate into prostaglandins E1 and F1 alpha compared to that into prostaglandins E2 and F2 alpha.     

Effects of prostaglandins on adrenal steroidogenesis in the rat

To elucidate the role of prostaglandins in adrenal steroidogenesis, we studied aldosterone and corticosterone responses to 3 x 10(-8) M--3 x 10(-4) M of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), prostacyclin (PGI2), and arachidonic acid (AA) in collagenase dispersed rat adrenal capsular and decapsular cells. Whereas adrenocorticotrophic hormone (ACTH) and angiotensin II (AII) stimulated aldosterone production in capsular cells and ACTH stimulated corticosterone production in decapsular cells in a dose dependent fashion, aldosterone and corticosterone production were not stimulated significantly by PGE2, PGF2 alpha, PGI2, and AA. Although preincubation of dispersed adrenal cells with indomethacin (3 x 10(-5) M) markedly inhibited PGE2 synthesis, ACTH- and AII-stimulated aldosterone production and ACTH-stimulated corticosterone production were not attenuated despite prostaglandin blockade. These results indicate that prostaglandins are unlikely to play an important role in adrenal steroidogenesis.     

Metabolism of prostaglandins D2 and F2 alpha in primary cultures of rat hepatocytes

3H-Labeled prostaglandins D2 and F2 alpha rapidly degraded to more-polar metabolites in primary cultured rat hepatocytes. The metabolites of prostaglandins D2 and F2 alpha accumulated in the culture medium. The metabolites extracted by ethyl acetate at pH 3 were purified by silicic acid column and thin-layer chromatography of silica gel, and were analysed by gas chromatography-mass spectrometry. The major metabolites from prostaglandin D2 were identified as dinor-prostaglandin D1 (7 alpha,13-dihydroxy-9-ketodinorprost-11-enoic acid) and tetranor-prostaglandin D1 (5 alpha,11- dihydroxy-7-ketotetranorprost-9-enoic acid). Those from prostaglandin F2 alpha were identified as dinor-prostaglandin F1 alpha (7 alpha,9 alpha,13-trihydroxydinorprost-11-enoic acid), tetranor-prostaglandin F1 alpha (5 alpha,7 alpha,11-trihydroxytetranorprost-9-enoic acid) and 9 alpha,11 alpha,15-trihydroxyprost-13-ene-1,20-dioic acid. These data indicate that prostaglandins D2 and F2 alpha mainly degraded by beta-oxidation, which is the same process as reported earlier for prostaglandins E1 and E2, and that prostaglandin F2 alpha was also subjected to omega-oxidation.     

Prostaglandin production by phagocytic cells of the mouse thymic reticulum in culture and its modulation by indomethacin and corticosteroids

The production of prostaglandins by phagocytic cells of the thymic reticulum in culture (P-TR) was studied by using high pressure liquid chromatography and radioimmunoassay. Radioimmunologic determinations showed that thromboxane B2 (TXB2), prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1 alpha (6 keto-PGF1 alpha) were the major compounds released into the culture medium, whereas prostaglandin F2 alpha (PGF2 alpha) was only a minor component. Indomethacin and dexamethasone exerted a similar pattern of differential inhibition of the secretion of prostanoids. PGE2 and 6-keto PGF1 alpha productions were markedly decreased by these anti-inflammatory drugs, whereas those of TXB2 and PGF2 alpha were not or were only slightly affected. Experiments performed with an antiglucocorticoid compound (RU 38486) showed that the steroid-induced inhibition of prostanoid secretion is a classical receptor-mediated action. These results demonstrated that phagocytic cells of the thymic reticulum, which resemble the thymic interdigitating cells, produce several types of prostaglandins. Because it has been described that P-TR regulate thymocyte proliferation in vitro via the secretion of both interleukin 1 and PGE2, these results suggest that anti-inflammatory agents may be able to modulate the thymic microenvironment and, consequently, thymocyte proliferation.     

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.     

Studies on closure of the ductus arteriosus. X. In vivo effect of prostaglandin.

The effect of prostaglandins F2alpha, E1 and of 7-oxa-13-prostynoic acid on the newborn rabbit ductus can be studied using the whole-body freezing technique. PGF2alpha and PGE1 were able to re-open the closing ductus arteriosus in adequately oxygenated animals. PGF2alpha administration was accompanied by a strong physical reaction in the rat but less in the rabbit. PGE1 had sedative effects in both animals. A prostaglandin antagonist, 7-oxa-13-prostynoic acid had no effect on normal ductal closure nor did it counteract the effects of PGF2alpha and PGE1. The role of prostaglandins in homeostasis during the fetal and newborn period may be to modify ductal tone.     

Urinary excretion of prostaglandins during infancy and childhood: influence of age, sodium restriction and posture

The influences of age, sodium restriction and posture on 24-hour urinary excretion of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF 2 alpha), 6-keto-prostaglandin F1 alpha (6-keto-PGF 1 alpha) and thromboxane B2 (TXB2) were investigated in 111 healthy children and youngsters in the age between 1 day and 16 years. A considerable degree of variation was found in normal 24-hour urinary prostaglandin excretion in all age groups. There was no significant effect of age on the urinary excretion of prostaglandins when data were corrected for body surface area. In addition, sodium restriction and posture had no influence on the excretion of PGE2, PGF 2 alpha, 6-keto-PGF 1 alpha and TXB2. Our results indicate that in the first days of life the kidney already has the capacity to synthesize prostaglandins in amounts comparable to older children.     

Role of gastric mucosa prostaglandins in the development of ulcer lesions in liver cirrhosis]

The amount of prostaglandins (PD) E, F2 alpha and I2 (measured as 6-keto-Pg F1 alpha) in endoscopic biopsy specimens of gastric corpus' mucosa also as the concentration of Pg E and F2 in gastric juice of cirrhotic patients without or with gastric and duodenal ulcer were measured by radioimmunoassay. Release of Pgs with gastric juice (in the basal state and after histamine stimulation) was also significantly less in these patients. It was concluded that the severe disturbance of endogenous biosynthesis Pgs in gastroduodenal mucus of cirrhotic patients may play an important role in the development of ulcer disease in these patients.