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Background and purpose:Agonists of the M2 muscarinic acetylcholine receptor (mAChR) increase mRNA for this receptor and mRNA for endothelial and neuronal isoforms of NO synthase (eNOS or nNOS). Here we examine the different signalling pathways involved in such events in rat cardiac atria.Experimental approach:In isolated atria, the effects of carbachol on mRNA for M2 receptors, eNOS and nNOS were measured along with changes in phosphoinositide (PI) turnover, translocation of protein kinase C (PKC), NOS activity and atrial contractility.Key Results:Carbachol increased mRNA for M2 receptors, activation of PI turnover, translocation of PKC and NOS activity and decreased atrial contractility. Inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), NOS and PKC prevented the carbachol-dependent increase in mRNA for M2 receptors. These inhibitors also attenuated the carbachol induced increase in nNOS- and eNOS-mRNA levels. Inhibition of nNOS shifted the dose response curve of carbachol on contractility to the right, whereas inhibition of eNOS shifted it to the left.Conclusions and implications:From our results, activation of M2 receptors induced nNOS and eNOS expression and activation of NOS up-regulated M2 receptor gene expression. The signalling pathways involved included stimulation of PI turnover via PLC activation, CaM and PKC. nNOS and eNOS mediated opposing effects on the negative inotropic effect in atria, induced by stimulation of M2 receptors. These results may contribute to a better understanding of the effects and side effects of cholinomimetic treatment in patients with cardiac neuromyopathy.British Journal of Pharmacology (2007) 151, 175–185. doi:10.1038/sj.bjp.0707180; published online 26 March 2007 [ABSTRACT FROM AUTHOR]

IgA was obtained from HlV-infected haemophilic patients and the intracellular signals triggered by its reaction with isolated rat intestinal strips were studied. HIV+IgA stained intestinal microvilli with a granular immunofluorescence pattern and bound to the muscarinic acetylcholine receptor (mAChR), displacing the specific muscarinic cholinergic antagonist QNB in a non-competitive manner. It triggered the signals that are the consequence of mAChR stimulation in the intestine. Thus, it decreased cAMP synthesis and increased guanosine 3':5'-cyclic monophosphate (cGMP) formation and phosphoinositide (PI) turnover of the intestine. In addition, it stimulated prostaglandin E2(PGE2) synthesis by intestinal strips. Through its effect on PGE2 synthesis. HIV+ IgA could have a dual action. On the one hand, it could enhance immunosuppression at a local level, favouring pathogen growth and subsequent intestinal dysfunction. On the other hand, PGE2 could directly increase intestinal motility and electrolyte/fluid loss. Both effects could be involved in intestinal damage in AIDS. [ABSTRACT FROM AUTHOR]

It this study we demonstrate that IgG present in the sera of patients with primary Sjögren's syndrome (PSS) could bind and activate muscarinic acetylcholine receptors (mAChRs) of rat parotid gland. These antibodies were able to inhibit in a non-competitive manner the binding of ³H-quinuclidinyl benzilate (QNB) to mAChRs of purified rat parotid gland membranes. Moreover, IgG from PSS could modify biological effects mediated by mAChR activation; i.e. decrease camp, increase phosphoinositide turnover without affecting cGMP. Atropine and 4-DAMP blocked all of these effects, and carbachol mimicked them, confirming the M3 subtype mAChRs mediated PSS IgG action. Neither binding nor biological effect were obtained with IgG from sera of normal women. The prevalence of cholinergic antibody was 100% in PSS, and was independent of Ro/SS-A and La/SS-B antibodies. It could be concluded that antibody against mAChRs may be another serum factor to be considered in the pathophysiology of the development of PSS. [ABSTRACT FROM AUTHOR]

The presence of serum autoantibodies in periodontitis (P) patients against beta(1)-adrenoceptor (beta(1)-AR), using cardiac membranes or a synthetic beta(1)-AR peptide corresponding to the second extracellular loop of human beta(1)-AR as antigens, permit us to detect circulating antibody from 40 P patients but not in 20 normal individuals (control). Simultaneously, the P patients exhibited a decrease in HRV. Anti-beta(1)-AR IgG titters correlated with the decrease in HRV of the same patients and the anti-beta(1)-AR peptide IgG displayed partial agonist-like activity and modified the contractility of isolated atria, produced cyclic nucleotides, and inhibited the beta(1)-AR agonistic activity of isoproterenol. We demonstrated in this study an association between periodontitis infection and an increased risk of cardiac disease, thereby highlighting the role of anti-beta(1)-AR autoantibodies in alteration of myocardial contractility. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate that circulating antibodies from chronic periodontitis patients reacting with atrial β(1)-adrenoceptors (β(1)-ARs) act as an inducer of soluble CD40 ligand (sCD40L) release and prostaglandin E(2) (PGE(2)) generation. By enzyme-linked immunosorbent assay using β(1) synthetic peptide (with an amino acid sequence identical to the second loop of human myocardial β(1)-ARs) as a coating antigen, we demonstrated reactivity against the second extracellular loop on human myocardial β(1)-ARs. This autoantibody present in the serum of chronic periodontitis patients was significantly correlated with the release of sCD40L and PGE(2). The release of sCD40L was blunted by atenolol, SP600125 and β(1) synthetic peptide, and PGE(2) generation was inhibited by DuP 697 and slightly by FR122049. The effects of the antibody incubated with isolated rat atria upregulated sCD40L release with an increase of PGE(2) production and c-Jun N-terminal kinase phosphorylation. These results indicate that in chronic periodontitis patients, there is a positive association between sCD40L release and PGE(2) generation via the action of β(1)-AR antibodies.

Background: Patients with primary Sjögren's syndrome (pSS) produce functional IgG against cholinoreceptor of exocrine glands modifying their activity. The aim of the present work was to demonstrate pSS IgG antibodies (pSS IgG) interacting with M(3) muscarinic acetylcholine receptors (mAChR) of rats submandibular glands that alter mucin release and production via phospholipase C (PLC) and cyclooxigenase-2 (COX-2) pathways., Methods: Mucin release and production of prostaglandin E2 (PGE2), and total inositol phosphates (InsP) were measured in rat submandibular gland in the presence of pSS IgG auto antibodies., Results: The auto antibodies interacting with M3 mAChR decreased mucin release and production through stimulation of PLC and COX-2. This stimulation leads to an incremental increase in InsP production and in PGE2 generation, inducing signalling through the prostaglandin membrane receptors subtype 2 (EP2). Moreover, the decrease in mucin production had negative correlation with PGE(2) generation and InsP accumulation., Conclusion: IgG in patients with pSS could play an important role in the pathoetiology of dry mouth, decreasing the salivary mucin through the production of proinflammatory substances and leading to the reduction in the protection of the oral tissues.

The presence of serum autoantibodies in periodontitis (P) patients against β(1)-adrenoceptor (β(1)-AR), using cardiac membranes or a synthetic β(1)-AR peptide corresponding to the second extracellular loop of human β(1)-AR as antigens, permit us to detect circulating antibody from 40 P patients but not in 20 normal individuals (control). Simultaneously, the P patients exhibited a decrease in HRV. Anti-β(1)-AR IgG titters correlated with the decrease in HRV of the same patients and the anti-β(1)-AR peptide IgG displayed partial agonist-like activity and modified the contractility of isolated atria, produced cyclic nucleotides, and inhibited the β(1)-AR agonistic activity of isoproterenol. We demonstrated in this study an association between periodontitis infection and an increased risk of cardiac disease, thereby highlighting the role of anti-β(1)-AR autoantibodies in alteration of myocardial contractility.

We demonstrated that circulating antibodies from schizophrenia patients, which interact with cerebral M1 muscarinic acetylcholine receptors (M1 mAChRs), trigger production of nitric oxide (NO), prostaglandin E2 (PGE2) and matrix metalloproteinase-3 (MMP-3), and act as inducers of cyclooxygenase-1 (cox-1) and inducible nitric oxide synthase (iNOS) mRNA expression in the rat frontal cortex. The corresponding affinity-purified anti-M1 peptide IgG from schizophrenia patients, while stimulating cerebral M1 mAChRs, increases NOS activity, PGE2 and MMP-3 production associated with iNOS over-activity and mRNA expression. Moreover, PGE2 and MMP-3 production is the result of cox-1 expression and activity. All these effects were inhibited by pirenzepine or haloperidol and mimicked the action of the authentic mAChR agonist. Concurrent analysis of the effects of iNOS, phospholipase C, protein kinase C and calcium/calmodulin inhibition showed that antibody up-regulation of NOS activity, PGE2 and MMP-3 production is under the control of the endogenous NO signalling system. These results provide evidence of the role that cholinergic receptor antibodies play in the development of cerebral inflammation, which shows that an antibody that interacts with cerebral mAChRs can induce expression of pro-inflammatory mediators, and support the participation of an autoimmune process in a particular group of chronic schizophrenia patients.

Objectives: To demonstrate the presence of circulating autoantibodies (Abs) from patients with chronic periodontitis (CP) that interacted with human gingival fibroblast membranes activating beta(1) adrenoceptors (beta(1)-AR)., Methods: Sera and purified IgG from 25 patients with CP and 20 age-matched healthy subjects were studied by flow cytometry, ELISA and DNA synthesis. Human gingival fibroblast membranes and/or synthetic peptides with amino acid sequences identical to human beta(1)-AR were used as antigens., Results: By flow cytometry and ELISA procedures, we proved that the serum-purified IgG fraction from patients with CP reacted with the fibroblast surface and to the beta(1) synthetic peptide. The corresponding affinity-purified anti-beta(1) peptide Abs displayed agonist-like activity associated with specific receptor activation, inhibiting the DNA synthesis of human gingival fibroblasts., Conclusions: This study demonstrates that beta(1)-AR autoantibodies are elevated in patients with CP. These autoantibodies were targeted to the fibroblasts, and specifically to the beta(1)-AR, and has receptor-like activity inhibiting DNA synthesis.

Chronic chagasic cardiomyopathy (CCC) is characterized mainly by a dilated cardiomyopathy complicated by frequent and complex ventricular arrhythmias and/or conduction defects. The aim of the present study was to evaluate functional implications of neurotransmitter receptor autoantibodies in vivo. Sera from chagasic patients were used to measure the level of autoantibodies to peptide fragments from the M2 cholinergic and beta1 adrenergic receptors. Optical density values and the frequency of anti-M2 and anti-beta1 antibodies were significantly higher in the indeterminate form and in CCC patients than in normal individuals. There was no correlation between levels of autoantibodies and clinical parameters of ventricular dysfunction, as assessed by echocardiography. Patients presenting with chronotropic insufficiency in exercise test had higher levels of anti-M2 but not anti-beta1 autoantibodies. Although anti-M2 and anti-beta1 antibodies do not appear to play a role in the pathophysiology of the heart failure that accompanies severe CCC, anti-M2 cholinergic autoantibodies may contribute to the pathogenesis of Chagas' disease dysautonomia.

Atria from mice fed a selenium-deficient (Se(-)) diet have a diminished beta-adrenoceptor-inotropic cardiac response to isoproterenol or norepinephrine compared with atria from mice fed the same diet supplemented with 0.2 mg/kg Se as sodium selenite (Se(+)). This diminished response could be reversed by feeding Se(-) mice the Se(+) diet for 1 wk or by pretreatment with nitric oxide synthase (NOS) inhibitors such as N(G)-monomethyl-l-arginine or aminopyridine. Elevated serum concentrations of nitrite/nitrate as well as a threefold increase in the atrial NOS activity were seen in the Se(-) versus Se(+) mice. Western blotting and indirect immunofluorescence indicated an enhanced expression of inducible NOS in hearts from Se(-) mice. Increased expression and activity of NOS and increased nitrite/nitrate levels from Se(-) mice correlated with an impaired response to beta-adrenoceptor inotropic cardiac stimulation. Elevated nitric oxide levels may account for some of the pathophysiological effects of Se deficiency on the heart.

Background: Histamine is released from mast cells by immunologic and non-immunologic stimuli during salivary gland inflammation, regulating salivary secretion. The receptor-secretory mechanism has not been studied in detail., Aims: The studies reported were directed toward elucidating signal transduction/second messenger pathways within the rat submandibular gland associated with 2-thiazolylethylamine (ThEA)-induced H(1)-receptor responses., Materials and Methods: To assess the H(1) receptor subtype expression in the rat submandibular gland, a radioligand binding assay was performed. The study also included inositolphosphates and cyclic GMP accumulation, protein kinase C and nitric oxide synthase activities, and amylase release., Results: The histamine H(1) receptor subtype is expressed on the rat submandibular gland with high-affinity binding sites. The ThEA effect was associated with activation of phosphoinositide-specific phospholipase C, translocation of protein kinase C, stimulation of nitric oxide synthase activity and increased production of cyclic GMP. ThEA stimulation of nitric oxide synthase and cyclic GMP was blunted by agents able to interfere with calcium movilization, while a protein kinase C inhibitor was able to stimulate ThEA action. On the other hand, ThEA stimulation evoked amylase release via the H1 receptor but was not followed by the L-arginine/nitric oxide pathway activation., Conclusions: These results suggest that, apart from the effect of ThEA on amylase release, it also appears to be a vasoactive chemical mediator that triggers vasodilatation, modulating the course of inflammation.

In this study we have determined the different signalling pathways involved in adenosine A(1)-receptor (A(1)-receptor)-dependent inhibition of contractility in rat isolated atria. N-cyclopentyladenosine (CPA) stimulation of A(1)-receptor exerts: negative inotropic response, inositol phosphates accumulation, stimulation of nitric oxide synthase (NOS), increased production of nitric oxide (NO) and cyclic GMP. Inhibitors of phospholipase C (PLC), protein kinase C (PKC), calcium/calmodulin, NOS and guanylate cyclase shifted the dose-response curve of CPA on contractility to the right. Those inhibitors also attenuated the A(1)-receptor-dependent increase in cyclic GMP and activation of NOS. These results suggest that CPA activation of A(1)-receptors exerts a negative inotropic effect associated with increased production of nitric oxide and cyclic GMP. The mechanism appears to occur secondarily to stimulation of phosphoinositide turnover via PLC activation. This, in turn, triggers cascade reactions involving calcium/calmodulin and PKC, leading to activation of NOS and soluble guanylate cyclase.

Purpose: The authors investigated whether circulating autoantibodies against M(3) muscarinic acetylcholine receptors (mAChRs) could be a new marker for diagnosis for primary and secondary Sjögren syndrome (SS) dry eye., Methods: Enzyme-linked immunosorbent assay (ELISA) using both rat exorbital lacrimal gland acinar cell membranes and synthetic 25-mer peptide as antigens was used to determine autoantibodies against acinar cells and M(3) mAChRs. Also, nitric oxide synthase (NOS) activity was assessed to determine the biological effect of these autoantibodies in relation to the M(3) mAChR., Results: Sera from dry eye primary SS (pSS) or secondary SS (sSS) patients tested by ELISA recognized membrane lacrimal gland acinar cells antigens and the synthetic 25-mer peptide, corresponding to the second extracellular loop of human M(3) mAChRs. Moreover, the IgG fraction and the corresponding affinity-purified anti-M(3) peptide autoantibodies from the same patients were able to activate NOS coupled to lacrimal gland M(3) mAChRs. As controls, IgG and sera from women without dry eye with or without rheumatoid arthritis and from normal control subjects gave negative results on ELISA and biological assay; thus demonstrating the specificity of the reaction., Conclusions: Autoantibodies against mAChR may be considered among the serum factors implicated in the pathophysiology of the development of pSS dry eyes and could be a new marker to differentiate SS dry eyes from non-SS dry eyes.

Purpose: The authors demonstrated that immunoglobulin G, present in the sera of patients with primary Sjögren syndrome (pSS), could recognize and activate muscarinic acetylcholine receptors (mAChRs) of rat exorbital acrimal gland., Methods: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and radioligand binding and biologic assays were used to demonstrate autoantibodies against mAChRs., Results: These autoantibodies recognized by means of SDS-PAGE and immunoblotting assay a band of approximately 70 kDa expressed on lacrimal gland membranes that comigrated with the peak of labeled mAChRs. Moreover, pSS IgG were able to inhibit, in an irreversible manner, the binding of [3H]quinuclidinyl benzilate to mAChRs of rat exorbital lacrimal glands and to simulate the biologic effect of mAChR agonists, because they trigger the activation of phosphoinositide turnover. Atropine and 4-diphenylacetoxy-N-methylpiperidine methiodide blocked the effect and carbachol mimicked it, confirming that the M3 subtype mAChRs mediated pSS IgG action. As control, IgG from sera of women without pSS gave negative results on immunoblotting, binding, and biologic assays, thus demonstrating the specificity of the reaction., Conclusions: Autoantibodies against mAChRs may be considered among the serum factors implicated in the pathophysiology of the development of pSS dry eyes.

1. In this paper we have determined the different signalling pathways involved in muscarinic acetylcholine receptor (AChR)-dependent inhibition of contractility in rat isolated atria. 2. Carbachol stimulation of M2 muscarinic AChRs exerts a negative inotropic response, activation of phosphoinositide turnover, stimulation of nitric oxide synthase and increased production of cyclic GMP. 3. Inhibitors of phospholipase C, protein kinase C, calcium/calmodulin, nitric oxide synthase and guanylate cyclase, shifted the dose-response curve of carbachol on contractility to the right. These inhibitors also attenuated the muscarinic receptor-dependent increase in cyclic GMP and activation of nitric oxide synthase. In addition, sodium nitroprusside, isosorbide, or 8-bromo cyclic GMP, induced a negative inotropic effect, increased cyclic GMP and activated nitric oxide synthase. 4. These results suggest that carbachol activation of M2 AChRs, exerts a negative inotropic effect associated with increased production of nitric oxide and cyclic GMP. The mechanism appears to occur secondarily to stimulation of phosphoinositides turnover via phospholipase C activation. This in turn, triggers cascade reactions involving calcium/calmodulin and protein kinase C, leading to activation of nitric oxide synthase and soluble guanylate cyclase.

The expression of beta-adrenergic receptors on murine lymphocytes stimulated with concanavalin A was studied. A decrease in beta-adrenoceptor number on T lymphocytes and a diminished response to specific agonist stimulation at the peak of proliferation was found. The blockade of cell proliferation by tyrosine kinases or protein kinase C inhibitors reversed the decrease in beta-adrenoceptor number. PMA plus ionophore or interleukin-2 but not PMA alone were able to induce beta-adrenoceptor down-regulation accompanying cellular proliferation. These results showed that the intracellular signals triggered during lymphocyte activation are involved in beta-adrenoceptor down-regulation and it would represent the loss of a mechanism that exerts negative neuroimmune control of cellular proliferation.

1. We have previously demonstrated a molecular relationship between laminin and cardiac cholinoceptors. 2. We have now explored the participation of cytoskeletal proteins in the interaction between an antilaminin IgG with cardiac cholinoceptors. 3. Antilaminin IgG, whilst it specifically reacts with laminin molecules was able to induce cardiac cholinoceptor activation; acting like an agonist, decreasing cyclic AMP concentrations, reducing heart contractility and increasing phosphoinositide turnover. 4. Antilaminin IgG also interfered with the binding of a radiolabelled muscarinic antagonist, [3H]-quinuclidinyl benzilate. Colchicine and cytochalasin B, drugs that are able to prevent microfilament and microtubule polimerization, impaired the binding of antilaminin IgG to muscarinic cholinoceptors. 5. Cytochalasin B but not colchicine modified the muscarinic cholinoceptor effects mediated by regulatory G proteins (cyclic AMP and contractility) induced by antilaminin IgG. 6. It was demonstrated, by immunofluorescence, that none of these disrupting drugs altered the specific recognition of the antibody by its antigen. 7. These data indirectly suggest the participation of the cytoskeleton in the laminin and cholinergic receptor association.

Recombinant rat interferon gamma stimulated the contractility of isolated rat ileum at doses of 4-12 units/ml. Muscarinic cholinoceptors were involved, as treatment of the tissue with atropine prevented the contractile response of the ileum. Furthermore, interferon gamma increased the affinity of carbachol for the cholinoceptors and did not change its maximum effect. Neurogenic pathways were also involved since pretreatment of ileum with hexamethonium, hemicholinium or tetrodotoxin impaired the contractile effect of interferon gamma. In contrast to the action of exogenous carbachol, the effects of interferon gamma are indirect. They appear to involve a G protein regulating phosphoinositide turnover and cytoskeletal structures since they could not be induced in ileum strips that were pretreated with pertussis toxin, phospholipase C inhibitors (2-nitro-carboxyphenyl, NN-diphenyl carbamate and neomycin), cytochalasine B or colchicine.

Stimulation of phosphoinositide hydrolysis in myocardium from autoimmune myocarditis mice by ThEA and histamine was assayed. Myocardium from autoimmune heart, but not the normal forms, specifically increased phosphoinositide turnover in the presence of histaminergic agonists. This increment was blocked by a specific H1 antagonist mepyramine and to the same extent by the phospholipase C inhibitor NCDC. By using a binding assay H1 histaminergic receptors were detected in autoimmune heart membrane preparations, but this was not observed in normal heart. These data suggest that autoimmune myocardium expressed a functional H1 receptor that could involve a distinctive mechanism operating in the disease.

Induction of polyphosphoinositide hydrolysis in cardiac tissue by specific recognition of class I histocompatibility antigens was assayed. C3H (H-2k) mice auricles were labelled with myo-[3H]inositol precursor and inositol phosphate production in the presence or absence of anti-class I k products was measured. Anti-class I, but not anti-class II products specifically increased phosphoinositide turnover. This increment was partially blocked by muscarinic cholinergic and alpha-adrenergic blockers and even more so by the phospholipase C inhibitor NCDC. Alloantibodies specifically directed against class I antigens could then exert stimulation of phospholipase C-mediated phosphoinositide hydrolysis through the interaction with muscarinic cholinergic and/or alpha-adrenergic receptors. The induction of intracellular second messengers by class I antigens and hormone-receptor interactions is discussed.

Normal human lymphocytes (4 X 10(5) ml-1) incubated with sodium arachidonate (8 X 10(-7)M) (NaA-L) induced a strong enhancement of the tension and frequency of spontaneously beating rat atria. Normal human lymphocytes (L) or NaA alone at 8 X 10(-7)M did not modify this contractile activity. Between 2 X 10(-6)M to 1 X 10(-5)M NaA alone increased the tension of the atria without effect on the rate. In the presence of L (4 X 10(5) ml-1) the dose-response curve to NaA shifted to the left, the potency and the efficiency of NaA were enhanced and the chronotropic action was triggered. Inhibitors of cyclo-oxygenase (indomethacin 1 X 10(-6)M or acetylsalicylic acid (ASA) 1.8 X 10(-4)M) completely blocked the positive inotropic effect induced by NaA alone. Inhibitors of lipoxygenase/s (nordihydroguaiaretic acid (NDGA) 1 X 10(-5)M or 5,8,11,14-eicosatetraynoic acid (ETYA) 1 X 10(-7)M did not modify this effect. Indomethacin and ASA did not block the positive inotropic and chronotropic effects of the lower concentration of NaA-L and significantly reduced the inotropic effect of the higher ones. NDGA and ETYA shifted to the right the inotropic and chronotropic dose-response curve to NaA-L. FPL-55712 (1 X 10(-7)M), the slow reacting substance of anaphylaxis (SRS-A) antagonist, significantly reduced the overall inotropic and chronotropic effect of NaA-L. Direct contact of NaA-L with the atria was not necessary. Cell-free supernatants of L exposed to NaA increased the tension and the frequency of beating rat atria. 7 The stimulatory effect of NaA-L supernatants did not occur if rat atria had been previously incubated with NDGA 1 x 10-5 M. On the other hand, the generation of stimulatory products from NaA-L was not prevented by preincubating L with 1 x 10-5 M NDGA. Hence SRS-A and/or other oxidative metabolites of arachidonic acid were produced by the atria. 8 These results suggest that NaA-L react in vitro with spontaneous beating rat atria, inducing inotropic and chronotropic effects. Moreover, the stimulatory action of NaA itself was potentiated by L. These reactions involved a balance between cyclo-oxygenase and lipoxygenase oxidative products with a central role for SRS-A.

The reactivity to methoxamine (Met) of atria isolated from the hearts of normal and from acutely streptozotocin-diabetic rats has been studied. Met (1 X 10(-6) M) increased the tension of both normal and diabetic atria, but in diabetic atria, the dose-response curve to Met was shifted to the left and the efficacy of Met was enhanced. Inhibitors of alpha-adrenoceptors blocked, in a competitive manner, the positive inotropic effect induced by Met in both types of atrial preparations. Inhibitors of the cyclo-oxygenase pathway for arachidonic acid metabolism blocked the atrial response to Met in non-diabetic as well as in diabetic atria. The inhibition of prostacyclin synthetase prevented the effect of Met in normal atria, while blockers of thromboxane generation inhibited it in diabetic ones. Agents that inhibit the activity of lipoxygenase(s) significantly reduced the positive inotropic action induced by Met in diabetic atria but failed to modify it in non-diabetic preparations. These results show that diabetic atria are more sensitive to Met than normal atria. In diabetes the response to alpha-adrenoceptor stimulation could be mediated by oxidative product generated via thromboxane synthetase and lipoxygenase(s) activities; whereas in normal preparations the action of Met may involve the release of prostacyclin.

Normal human lymphocytes (L) (8 X 10(5) ml-1) incubated with methoxamine (Me) (1 X 10(-7) M) (Me-L) triggered the mechanical response of the isolated vas deferens of the rat. L or Me alone did not modify this contractile activity at the concentrations cited above. Me alone (10(-6) to 10(-3) M) increased the tension of the vas. In the presence of L (8 X 10(5) ml-1) the dose-response curve to Me shifted to the left and the efficacy of Me was enhanced. Inhibitors of alpha 1-adrenoceptors completely blocked the reaction between Me and L while drugs that block alpha 1 and alpha 2-adrenoceptors reduced the reaction between Me-L and the vas deferens. Direct contact of Me-L with the assay organ was not necessary. Cell-free supernatants of L exposed to Me (Me-L supernatants) elicited the reaction in the same way as Me-L. This effect required the continuous presence of Me since dialyzed Me-L supernatants were inactive. Inhibitors of lipoxygenase(s) completely blocked the positive inotropic effect of Me-L or of Me-L supernatants. Inhibitors of cyclo-oxygenase potentiated this effect. These results suggest that Me reacts with alpha 1-adrenoceptors of L. From this reaction, soluble factors are released that potentiate the alpha-adrenoceptor stimulatory effect of Me on the vas deferens as a consequence of the release of oxidative products of the lipoxygenase/s pathway of arachidonic acid.

Ovaries isolated from rats in different stages of the sex cycle were explored for spontaneous or drug-induced contractile activity. The number of spontaneously active ovaries as well as the magnitude of the isometrically developed tension and frequency of contractions were greater during the periovulatory interval (late proestrus and estrus) than during early proestrus or metestrus. Furthermore, during estrus or late proestrus the left ovaries exhibited a mechanical activity significantly greater than that of the right ovaries. The oxytocin-triggered motility was clearly more marked immediately prior to ovulation (late proestrus) and greater in left ovaries than in right ovaries. In contrast, the contractions induced by prostaglandin F2alpha were similar during early proestrus and late proestrus. Ovarian contractile reactivity to norepinephrine indicated the presence in the tissue of alpha- and beta-adrenergic receptors. During early proestrus this agent stimulated the motility of left and right ovaries, whereas close to the ovulatory interval (late proestrus) it depressed the contractions of left ovaries. This last influence was blocked by propranolol. The existence of a close relationship between ovarian contractile activity and ovulation is reinforced by the present results in the rat. A tentative participation of oxytocin is also suggested. In addition, the influences of other possible regulatory agents of ovarian contraction, such as catecholamines and prostaglandins, are presented and discussed.

Evidence accumulated over the last decade concerning human and experimental models suggests that an immunopathological mechanism may be involved in the pathogenesis of chronic Chagas' disease. In this paper we demonstrate the existence of two different circulating IgG in chagasic patients which bind with myocardial beta 1 and spleen cell beta 2 adrenoceptors, acting as non-competitive inhibitors. Both chagasic IgG against beta 1 and beta 2 adrenoceptor increased intracellular levels of cAMP that could be blocked by specific beta 1 and beta 2 adrenoceptor antagonists. The specificity for beta 1 and beta 2 adrenoceptors and the independence of other tissue reactive antibodies was demonstrated by IgG absorption with turkey red blood cell (TRBC), human lymphocytes (HL) or guinea pig red blood cells (GPRBC). The F(ab')2 fraction acted similarly. This supports the specificity of beta 1 and beta 2 adrenoceptors to the chagasic IgG and the independence of the other tissue reactive antibodies, such as EVI system. The probable pathogenic role of both beta 1 and beta 2 adrenergic chagasic antibody is discussed.