Tricyclic antidepressants antagonize prostaglandin (PG) E2-induced contractions of the guinea pig ileum and hypomotility in the mouse

The interactions of PGE2 and 2 tricyclic antidepressants were tested both on the guinea pig ileum and motility in the mouse. PGE2-induced contractions of the guinea pig ileum were irreversibly blocked by amitriptyline and desipramine. Chronic administration of amitriptyline and desipramine blocked PGE2-induced hypomotility in the mouse.     

Interaction between PGE2 and EGF receptor through MAPKs in mouse embryonic stem cell proliferation

Identifying the small molecules that permit precise regulation of embryonic stem (ES) cell proliferation should further support our understanding of the underlying molecular mechanisms of self renewal. In the present study, we showed that PGE₂ increased [³H]-thymidine incorporation in a time and dose dependent manner. In addition, PGE₂ increased the expression of cell cycle regulatory proteins, the percentage of cells in S phase and the total number of cells. PGE₂ obviously increased E-type prostaglandin (EP) receptor 1 mRNA expression level compare to 2, 3, 4 subtypes. EP1 antagonist also blocked PGE₂-induced cell cycle regulatory protein expression and thymidine incorporation. PGE₂ caused phosphorylation of protine kinase C, Src, epidermal growth factor (EGF) receptor, phosphatidylinositol 3-kinase (PI3K)/Akt phosphorylation, and p44/42 mitogen-activated protein kinase (MAPK), which were blocked by each inhibitors. In conclusion, PGE₂-stimulated proliferation is mediated by MAPK via EP1 receptor-dependent PKC and EGF receptor-dependent PI3K/Akt signaling pathways in mouse ES cells. Received 30 January 2009; received after revision 03 March 2009; accepted 10 March 2009     

Effects of a new cholecystokinin antagonist (GE 410) on the smooth muscle of the guinea pig ileum

Summary Suc-Tyr-(SE)-Met-Gly-Trp-Met-Asp--phenethylamide (GE 410) competitively antagonized the contractions of smooth muscle strips from guinea pig ileum (pA₂=7.6, n=0.95) induced by cholecystokinin-octapeptide (CCK8). GE 410 inhibited the electrically-induced cholinergically mediated contractile responses and the [³H]ACh release in the ileum, as well as the CCK-stimulated electrical contractile responses and the [³H]ACh release in the cholinergic nerve terminals. The results suggest the existence of CCK-receptors not only in the smooth muscles but also on the neurons.     

Production of active and passive anaphylactic shock in the WBB6F1 mouse,a mast cell-deficient strain

Summary The role of mast cells in active and passive anaphylactic shock was examined using the WBB6F₁ mouse, a genetically mast cell-deficient strain. Lethal anaphylactic shock occurred at high incidence rates in mice actively sensitized to bovine serum albumin (BSA). The reaction was specific to BSA since the shock could not be elicited by human or guinea pig serum albumin in these animals. Lethal shock could be prevented by CV-3988 but not by cyproheptadine, which suggests that the shock is mediated by PAF but not by histamine and serotonin. Similarly, lethal shock was provoked by homologous antigens in mice which had been passively sensitized with allogeneic anti-benzylpenicilloyl (BPO) IgG₁ monoclonal antibody or with allogeneic or xenogeneic anti-BSA antiserum, but not in those sensitized with allogeneic anti-BPO IgE monoclonal antibody. These findings suggest that mast cells are not necessarily required for anaphylactic shock in the mouse.     

Prostaglandin-like substances inPropionibacterium acnes. V. Activity profiles using cascade superfusion bioassay and platelet aggregation

Summary The activity spectrum of prostaglandin-like substances (PLS) fromP. acnes was investigated with cascade superfusion technique and by platelet aggregation assay. The biological activity of PLS resembles that of PGI₂: both relax bovine coronary artery, rabbit mesentric and coeliac arteries; both contract the rat stomach strip as well as both typically inhibit spontaneous movements of isolated guinea pig ileum. Also, similarly to PGI₂, PLS inhibits platelet aggregation regardless the inducer used. However, PLS possesses a specific antiaggregatory pattern on platelet, which indicates that these compounds are not indentical with primary prostaglandins or PGI₂.     

A novel interplay between membrane and nuclear melatonin receptors in human lymphocytes: significance in IL-2 production

Human lymphocyte melatonin, through membrane and nuclear receptors binding, acts as an activator in IL-2 production. Antagonism of membrane melatonin receptors using luzindole exacerbates the drop of the IL-2 production induced by PGE₂ in peripheral blood mononuclear and Jurkat cells. This paper studies the melatonin membrane and nuclear receptors interplay in PGE₂-diminished IL-2 production. The decrease in IL-2 production after PGE₂ and/or luzindole administration correlated with downregulation in the nuclear receptor RORα. We also highlighted a role of cAMP in the pathway, because forskolin mimicked the effects of luzindole and/or PGE₂ in the RORα expression. Finally, a significant RORα downregulation was observed in T cells permanently transfected with inducible MT₁ antisense. In conclusion, we show a novel connection between melatonin membrane receptor signalling and RORα expression, opening a new way to understand melatonin regulation in lymphocyte physiology. Received 23 September 2008; received after revision 19 November 2008; accepted 21 November 2008     

Role of 5-hydroxytryptamine in prostaglandin E1-induced potentiation of hexobarbitone hypnosis in albino rats

Summary PGE₁ potentiated, while diclofenac, a prostaglandin synthesis inhibitor, antagonized hexobarbitone hypnosis in rats. PGE₁-induced potentiation of hexobarbitone sleep was inhibited by a 5HT synthesis inhibitor and by a 5HT receptor blocker, suggesting that this potentiation is 5HT mediated.Acknowledgment. The gift of the following drugs are gratefully acknowledged: PGE₁ (Dr.J. E. Pike, Upjohn), diclofenac (Ciba-Geigy), methysergide (Sandoz) and hexobarbitone (Bayer).     

A marine mollusc provides the first example of in vivo storage of prostaglandins: Prostaglandin-1,15-lactones

Summary Prostaglandin-(PG) 1,15-lactones and, in smaller amounts, free acids, were isolated from both the mantle and the dorso-lateral appendices of the opisthobranch molluscTethys fimbria. In vivo conversion of PGs into the corresponding lactones and accumulation of PGE₂- and PGE₃-1,15-lactones in the appendages were shown. The detachment of these appendages from the molested mollusc caused the in vivo conversion of PGE₂- and PGE₃-lactones back to PGE₂ and PGE₃ respectively, thus providing the first example of a mechanism by which prostaglandins can be stored and, when needed, released.     

Prostaglandin E1 induced salivary secretion

Summary PGE₁ but not PGF₂ at 500–1000 g/kg induced a slow and sparse flow from the parotid and no flow at all from submaxillary glands. Composition of PGE₁-induced parotid saliva was quite different from that evoked by any autonomic agonists. The present study suggests that PGE₁ might act directly on parotid acinar cells.Acknowledgment. This work was supported by NIDR grant DE05633. The authors wish to thank Ms Sonya Wynn for her technical assistance.     

Purification and some properties of hemagglutinin from the Myxomycete,Physarum polycephalum

A new hemagglutinin was isolated from the plasmodium ofPhysarum polycephalum by salting out with ammonium sulphate followed by chromatography on DE-32, DEAE-Toyopearl and hydroxyapatite. This hemagglutinin, named physarumin, was purified 1000-fold over crude extracts. The molecular weight of physarumin was determined to be 22,000 by size exclusion chromatography on Bio-Gel P-60 and 8,700 by SDS-polyacrylamide gel electrophoresis. Physarumin agglutinated rabbit, guinea pig, horse and human erythrocytes. Physarumin-induced hemagglutination was inhibited by fetuin and ₁ glycoprotein, but not by commercially available mono-and disaccharides. Hemagglutinating activity was blocked by EDTA, and was restored by adding Ca²⁺ but not by Mg²⁺.     

Versuche zur chromatographischen Trennung der im Augenstiel vonAstacus astacus enthaltenen myotropen Wirkstoffe

Summary The detection of two myotropic substances in the eyestalk and the brain of the crayfishAstacus astacus and the shrimpCrangon crangon was described². Both substances have an action on the isolated ileum of the guinea pig. The substance extracted from the eyestalk has a positive myotropic one, the substance extracted from the brain an inhibiting one.Further a method is given for the separation and purification of the positive myotropic substance of the eyestalk by paper-chromatography.     

The effect of ion pair formation on the antimuscarinic activity of methantheline

Summary The quaternary ammonium compound, methantheline, was found to antagonize acetylcholine induced contractions in isolated guinea pig ileum by a mechanism which did not conform to the criteria for either competitive or non-competitive inhibition. Enhancement of the lipid solubility of methantheline by formation of an ion pair with trichloracetate failed to influence its cholinergic inhibitory activity. The results suggest that in the guinea pig ileum a) an intracellular site of action does not exist for methantheline and b) the membrane receptors for methantheline most likely are located in an aqueous environment.     

The effect of ion pair formation on the antimuscarinic activity of methantheline.

The quaternary ammonium compound, methantheline, was found to antagonize acetylcholine induced contractions in isolated guinea pig ileum by a mechanism which did not conform to the criteria for either competitive or non-competitive inhibition. Enhancement of the lipid solubility of methantheline by formation of an ion pair with trichloracetate failed to influence its cholinergic inhibitory activity. The results suggest that in the guinea pig ileum a) an intracellular site of action does not exist for methantheline and b) the membrane receptors for methantheline most likely are located in an aqueous environment.     

Serum and bile modifications in the guinea-pig following chronic treatment with PGE1 and PGE2

Summary PGE₁ increases cholesterolemia without lipemia modifications. In bile there are not modifications in cholesterol levels and total lipids appear diminished. PGE₂ raise the lipemia and have no effect in cholesterolemia, moreover bile cholesterol and total lipids exhibit no changes. Both PGE₁ and PGE₂ decreased the bile volume.Acknowledgment. The authors wish to express their thanks to the Upjohn Laboratory for kindly furnishing the prostaglandins employed, with the relevant bibliography, and to Mr.F. A. Mori for the English translation.     

Influence of prostaglandins E1 and E2 on coagulation of rat blood

Zusammenfassung Die Prostaglandine E₁ (PGE₁) und E₂ (PGE₂) haben keinen Einfluss auf die Gerinnung von Rattenblut. Im Gegensatz zu früheren Postulationen können die Ca-Ionen im Plasma nicht von PGE₁ ersetzt werden. PGE₁ beeinflusst die maximale Amplitude des Thrombelastogramms in vitro nach Zugabe von 0.3–6 g/ml, während PGE₂ diesen Effekt nicht aufweist.     

A tissue-selective prostaglandin E2 analog with potent antifertility effects

Summary N-methanesulfonyl 16-phenoxy--tetranor PGE₂ is a prostaglandin analog which is markedly more tissue selective than PGE₂. This compound is 10–30 times more potent than PGE₂ in animal models which are considered relevant to antifertility effects in humans. In pharmacological tests which are believed to be predictive for side effects in humans, the compound has potency either equal to or less than that of PGE₂.     

Efficacy of tumor cell vaccine after incorporating monophosphoryl lipid A (MPL) in tumor cell membranes containing tumor-associated ganglioside

Murine B16 melanoma expresses the ganglioside. GM₃. GM₃ shed from tumor cells is immunosuppressive and promotes tumor growth¹. Reduction or elimination of the shed GM₃ could be therapeutic, and the anti-GM₃ antibodies may reduce and clear the shed ganglioside. To test this hypothesis, mice were challenged with tumor cells, with or without inducing anti-GM₃ antibody response. Since gangliosides are poor immunogens and T-cell independent antigens, an adjuvant (monophosphoryl lipid A (MPL), a non-toxic lipid A ofSalmonella), directed against B-cells, was employed. MPL was incorporated onto liposomes and into the surface membrane of B16 mouse melanoma cells; both are rich in GM₃. C57BL/6J mice immunized with MPL-liposomes or MPL-B16 cells responded with elevated levels of anti-GM₃ IgM. Non-immunized mice or mice immunized with B16 cells alone or ganglioside GM₃ alone (without MPL) elicited poor anti-GM₃ IgM response, confirming the GM₃'s immunologic crypticity and MPL's immunopotentiating effect. MPL's immunopotentiating effect was improved by coupling it to melanoma cell membranes C57BL/6J mice were immunized with irradiated B16 alone or MPL alone or MPL-conjugated irradiated B16. After three weekly immunizations, each mouse received a challenge dose of viable syngeneic B16. Neither MPL alone nor B16 alone had a significant effect on tumor growth or host survival; however, administration of MPL-conjugated B16 cells significantly prevented tumor growth and prolonged survival. Our results indicate that MPL-incorporated B16 cells augment the anti-GM₃ IgM response, which may reverse GM₃-induced immunosuppression by eliminating tumor-derived GM₃, and restore immunocompetence.     

Effects of a new cholecystokinin antagonist (GE 410) on the smooth muscle of the guinea pig ileum

Suc-Tyr-(SE)-Met-Gly-Trp-Met-Asp-beta-phenethylamide (GE 410) competitively antagonized the contractions of smooth muscle strips from guinea pig ileum (pA2 = 7.6, n = 0.95) induced by cholecystokinin-octapeptide (CCK8). GE 410 inhibited the electrically-induced cholinergically mediated contractile responses and the [3H]ACh release in the ileum, as well as the CCK-stimulated electrical contractile responses and the [3H]ACh release in the cholinergic nerve terminals. The results suggest the existence of CCK-receptors not only in the smooth muscles but also on the neurons.     

Opposite effect of PGE2 on cAMP levels in human adrenal medulla and pheochromocytoma

Summary PGE₂ (10^–7 M) caused increased cAMP accumulation in 5 pheochromocytomas, while in 3 human adrenal medullae PGE₂ caused a significant decrease of cAMP level on incubating slices in vitro. This finding is discussed in relation to the opposite effect of PGE₂ on catecholamine release from human medulla and pheochromocytoma slices in vitro.Acknowledgment. This paper is part of a Ph. D. thesis of Punya Boonyaviroj.Established Investigator of the Chief Scientist's Bureau, Israeli Ministry of Health.     

Alterations in the fraction of oxygen in inspired gas affect rates of renal prostaglandin E2 synthesis in anesthetized dogs

Summary Reductions of oxygen in inspired gas from 20% to 15%, in anesthetized dogs, reduced arterial PO₂ and increased the renal efflux of PGE₂ but not PGF_2a . Renal blood flow, blood pressure, plasma renin activity as well as arterial pH and PCO₂ were unaffected. PGs may mediate the renal hemodynamic or excretory consequences of alterations in PO₂. In addition, minor variations in PO₂ might account, in part, for the variable renal venous PGE₂ concentrations reported under basal conditions.Authentic prostaglandins were supplied by Dr John E. Pike of the Upjohn Company. This work was supported by grants from the Veterans Administration, the Southern Medical Association and U.S. Public Health Service. Dr. Brash is an American Heart Association, Missouri Affiliate Fellow.