The involvement of platelet activating factor in ovulation.

Follicle rupture during ovulation is associated with inflammation-like changes. Because platelet activating factor (PAF) participates in the inflammatory process, the effect of a PAF-specific antagonist, BN52021, on the ovulatory response was tested in rats. BN52021, administered locally, inhibited follicle rupture in rats stimulated to ovulate with human chorionic gonadotropin (hCG). In addition to suppressing rupture of the follicles, this antagonist suppressed the hCG-stimulated increase in ovarian collagenolysis and vascular permeability. The inhibition of ovulation of BN52021 could be reversed by simultaneous administration of PAF. Furthermore, PAF partially reversed the blockage of ovulation by inhibitors of eicosanoid synthesis. Collectively, these results suggest the involvement of PAF in ovulation. Its role seems to be closely related to the metabolism of arachidonic acid. Thus, modulation of PAF action may serve as an additional target for regulation of reproduction via its action on ovulation.

Loss of endothelium-dependent relaxant activity in the pulmonary circulation of rats exposed to chronic hypoxia.

To determine whether exposure to chronic hypoxia and subsequent development of pulmonary hypertension induces alterations of endothelium-dependent relaxation in rat pulmonary vascular bed, we studied isolated lung preparations from rats exposed to either room air (controls) or hypoxia (H) during 1 wk (1W-H), 3 wk (3W-H), or 3W-H followed by 48 h recovery to room air (3WH + R). In lungs pretreated with meclofenamate (3 microM), the endothelium-dependent vasodilator responses to acetylcholine (10(-9)-10(-6) M) and ionophore A23187 (10(-9)-10(-7) M) were examined during conditions of increased tone by U46619 (50 pmol/min). Acetylcholine or A23187 produced dose-dependent vasodilation in control lungs, this response was reduced in group 1W-H (P less than 0.02), abolished in group 3W-H (P less than 0.001), and restored in group 3WH + R. In contrast, the endothelium-independent vasodilator agent sodium nitroprusside remained fully active in group 3W-H. The pressor response to 300 pM endothelin was greater in group 3W-H than in controls (6.8 +/- 0.5 mmHg vs. 1.6 +/- 0.2 mmHg, P less than 0.001) but was not potentiated by the endothelium-dependent relaxing factor (EDRF) antagonists: hydroquinone (10(-4) M); methylene blue (10(-4) M); and pyrogallol (3 x 10(-5) M) as it was in controls. It was similar to controls in group 3W-H + R. Our results demonstrate that hypoxia-induced pulmonary hypertension is associated with a loss of EDRF activity in pulmonary vessels, with a rapid recovery on return to a normoxic environment.

Decreased leukotriene B4 synthesis in smokers' alveolar macrophages in vitro.

Recent studies have shown that alveolar macrophages (AM) are able to release leukotrienes (LTs). Since cigarette smoking inhibits the cyclooxygenase pathway of arachidonic acid metabolism in the AM, we evaluated the LT production by AM from smokers and nonsmokers. AM were obtained from 35 volunteers, 16 nonsmokers, and 19 smokers. The cells were incubated under various conditions including stimulation with 30 microM arachidonic acid, 2 microM ionophore A23187, or both. Each experiment was performed in parallel using cells from a smoker and a nonsmoker. Lipoxygenase products were analyzed by reverse-phase high performance liquid chromatography. After stimulation, nonsmokers' AM produced LTB4 and 5-hydroxy-eicosatetraenoic acid (5-HETE). In incubations of AM with arachidonic acid and ionophore, the amounts of products formed were: LTB4, 317 +/- 56 pmol/10(6) cells and 5-HETE, 1,079 +/- 254, mean +/- SEM. No metabolites were generated under control conditions (no stimulation). In all incubations performed, the peptido-LTs (LTC4, LTD4, and LTE4) were undetectable. In comparison with AM from nonsmokers, those from smokers showed a 80-90% reduction of 5-HETE and LTB4 synthesis (P less than 0.05 to P less than 0.001 according to stimulatory conditions). This defective lipoxygenase metabolite production in AM from smokers was observed over a wide range of stimuli concentrations and incubation times; AM from smokers also had lower levels of intracellular (esterified) 5-HETE than nonsmokers' AM. We also studied blood polymorphonuclear leukocytes (PMNL) and no difference in the synthesis of 5-lipoxygenase products in these cells was noticed between smokers and nonsmokers. These data show that cigarette smoking causes a profound inhibition of the 5-lipoxygenase pathway in AM but not in blood PMNL.

Atrial natriuretic factor in chronic obstructive lung disease with pulmonary hypertension. Physiological correlates and response to peptide infusion.

To investigate the physiological role of atrial natriuretic factor (ANF) in patients with hypoxic pulmonary hypertension secondary to chronic obstructive lung disease (COLD), we infused synthetic alpha-human ANF in seven such patients, and investigated the physiological correlates to circulating peptide levels in 24 patients with COLD. ANF infusion, at incremental rates of 0.01, 0.03, and 0.1 micrograms/kg.min, increased basal plasma immunoreactive (ir) ANF (136 +/- 38 pg/ml) by 3-, 10-, and 26-fold, respectively, and reduced pulmonary artery pressure (from 33 +/- 3 to 25 +/- 2 mmHg, P less than 0.001) and systemic arterial pressure (from 88 +/- 4 to 79 +/- 4 mmHg, P less than 0.001) in a dose-related fashion. Cardiac index increased by 13.5% (P less than 0.01) while heart rate was unchanged. Cardiac filling pressures decreased at 0.1 micrograms/kg.min ANF. Pulmonary and systemic vascular resistance fell by 37% (P less than 0.001) and 19% (P less than 0.001), respectively. Arterial oxygenation was impaired during ANF infusion, suggesting partial reversal of hypoxic pulmonary vasoconstriction. Plasma renin activity remained unchanged but aldosterone fell by 44% (P less than 0.01). The levels of plasma irANF in 24 patients correlated directly with the degree of hemoconcentration (r = 0.67, P less than 0.001), respiratory acidosis (r = -0.65, P less than 0.001), and pulmonary hypertension (r = 0.52, P less than 0.01). The results suggest that ANF may serve as a potent pulmonary vasodilator involved in the circulatory homeostasis of patients with COLD.

Tumor cell kinetics following antineoplastic ether phospholipid treatment.

Ether phospholipids are analogues of the naturally occurring 2-lyso-phosphatidylcholine that have been reported to have in vitro/in vivo antitumor activity. Their antiproliferative effect has been found against a variety of animal and human tumor cell lines. We have characterized the cytostatic activity of two ether phospholipids, 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and 1-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine, on a human tumor cell line derived from a colon adenocarcinoma, HT29. We have used three different flow cytometric approaches to study which phase of the cell cycle was the most sensitive to the antiproliferative activity of the two ether phospholipids. By applying the biparametric analysis, 5'-bromo-2-deoxyuridine incorporation versus DNA content, we have been able to demonstrate that ether phospholipids do not interfere with the S phase of the cell cycle. The simultaneous measurement of total nuclear protein versus DNA content in isolated HT29 nuclei has enabled us to exclude a block in the M phase of the cell cycle. Finally, the stathmokinetic analysis has allowed us to show that the cytostatic activity of the two ether phospholipids 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and 1-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine is characterized by multiple "terminal points" as the drugs action results in a G1 block and in a slow-down of the transition from late S to G2, followed by an accumulation of HT29 cells in the G2 phase of the cell cycle.

[Diagnostic value of selective anorexia in pathological weight loss]. / Évaluation de l'apport diagnostique des anorexies sélectives au cours des amaigrissements pathologiques.

PURPOSE: The diagnostic value of selective anorexia is debated. Some authors have suggested an association between meat aversion and cancer, but most do not use it as a diagnostic tool. We aimed to characterize anorexia of different diseases to search for an association between selective aversions and diagnostic groups. METHODS: All the patients admitted to three departments of a teaching hospital were included consecutively for 22months if they had more than 10 % weight loss in less than one year. Patients were excluded if history taking was not reliable, or if they suffered from anorexia nervosa. We compiled diagnoses at discharge and validated them six months later. We used logistic regression to identify independent factors associated with selective anorexia. RESULTS: Inclusion criteria were met in 106patients (female 44 %, median age 65years). Most frequent diagnoses were: cancer (36 %), infection (35 %), digestive diseases (19 %), non organic diseases (21 %). Recent selective anorexia was found in 46 % of the cases. It was significantly associated with female gender (P=0.002), marginally with young age (P=0.069) and long duration of weight loss (P=0.079). Opioid use at admission was negatively associated with selective anorexia (P=0.001). No specific diagnostic category was found to be associated. CONCLUSION: Selective anorexia does not appear to be a useful symptom to investigate pathological weight loss. It behaves more like a non-specific reactivation by current disease of earlier latent personal food aversions.

Factors associated with 12 week case-fatality in Staphylococcus aureus bacteraemia: a prospective cohort study.

Staphylococcus aureus bacteraemia (SAB) is a frequent and deadly disease. Given the lack of a randomized trial, optimal first-line antibiotic treatment is still debated. Our aim was to identify prognostic factors in SAB patients and to analyse the impact of first-line antibiotics. The VIRSTA prospective cohort study was conducted in eight tertiary care centres in France. Consecutive incident adults in whom a blood culture drawn in participating centres grew S. aureus between April 2009 and October 2011 were prospectively followed for 12 weeks. Factors associated with 12-week case-fatality were identified by multivariate logistic regression. We enrolled 2091 patients and analysed survival in 1972 (median age 67.8 years, interquartile range 55.5-78.9; females 692/1972, 35.1%). SAB was nosocomial or healthcare-related in 1372/1972 (69.6%) of cases and the primary focus was unknown in 414/1972 (21.0%) of cases. Week 12 case-fatality rate was 671/1972 (34.0%). The main independent prognostic factors on multivariate analysis were age (adjusted OR by 10-year increment 1.56; 95% CI 1.44-1.69), septic shock (OR 5.11; 95% CI 3.84-6.80), metastatic cancer (OR 4.28; 95% CI 2.88-6.38), and unknown primary focus (OR 2.62; 95% CI 2.02-3.41). In the 1538 patients with methicillin-sensitive S. aureus (MSSA) bacteraemia, first-line empiric antistaphylococcal penicillins (OR 0.40; 95% CI 0.17-0.95) and vancomycin (OR 0.37; 95% CI 0.17-0.83), alone or combined with an aminoglycoside, were associated with better outcome compared with other antibiotics. There are few modifiable prognostic factors for SAB. Initiating empiric antibiotics with antistaphylococcal penicillins or vancomycin may be associated with better outcome in MSSA bacteraemia.

Characterization of glucocorticoid inhibition of antigen-induced inositolphosphate formation by rat basophilic leukemia cells: possible involvement of phosphatases.

The suppressive effect of glucocorticoids (GC) upon antigen-induced phosphatidylinositol phospholipase C (PI-PLC) activity and inositol phosphate formation by rat basophilic leukemia cells (RBL-2H3) has been characterized. Addition of antigen for a period of 1-30 min enhanced production of [3H]inositol monophosphate (IP1), inositol 1,4-bisphosphate (IP2) and inositol 1,4,5-trisphosphate (IP3) by about 5-10-fold. Pretreatment with hydrocortisone (HC) reduced formation of the various inositol phosphates (IPs) and degradation of phosphatidylinositol 4,5-bisphosphate (PIP2) by an average of 50%. Maximal inhibition of hydrolysis of PIP2 and reduction in stimulation of IP3 formation was reached after 4 h of preincubation with 2.10(-6) M of HC. Cycloheximide and RU486, a GC receptor antagonist, completely prevented the inhibitory effect of HC on IP formation. Other GC, dexamethasone (DEX) and triamcinolone (each at 2.10(-7) M) markedly suppressed antigen induced IP3 production, while aldosterone and sex steroids such as estradiol and progesterone (each at 2.10(-6) M) were virtually inactive. Antigen-stimulated phosphorylation of a 18 kDa and other proteins was inhibited by about 60% following pretreatment with the GC. This inhibition was in turn prevented by cycloheximide. DEX also doubled the activity of cellular acid phosphatase activity. The results suggest that the inhibitory effect of GC is specific, receptor-mediated, dependent on protein synthesis and possibly mediated by protein phosphatase activity.

Changes in resident rat peritoneal macrophage eicosanoid release, induced by altering the buffer K+/Na+ ratio, are Ca2+ dependent.

Altering the buffer K+/Na+ ratio ([K+]o/[Na+]o) resulted in a biphasic change in the basal release of prostaglandin E2, 6-ketoprostaglandin F1 alpha (the stable breakdown product of prostaglandin I2) and thromboxane B2 (the stable metabolite of thromboxane A2), from resident rat peritoneal macrophages. Changing the [K+]o (at the expense of [Na+]o) from 15 mM to 0 mM or 75 mM (combined concentration of [K+]o and [Na+]o was maintained at 150 mM) resulted in a stimulation of 6-ketoprostaglandin F1 alpha and thromboxane B2 release. Prostaglandin E2 synthesis was also stimulated when the [K+]o was decreased from 15 mM to 0 mM. When the [K+]o was increased to 45 mM, prostaglandin E2 formation was inhibited but returned to values observed at 15 mM K+ when the [K+]o was further increased to 75 mM. Prostaglandin E2 synthesis at 75 mM K+ was still only 40% of that measured in the absence of K+, however. When cells were incubated in a Ca2+-free medium (+EDTA) eicosanoid release was drastically reduced and the changes in arachidonic acid metabolite release observed on changing the buffer [K+]o/[Na+]o were abolished. Total release of radiolabel ([14C]arachidonic acid and its radiolabelled metabolites) from macrophages prelabelled with [14C]arachidonic acid followed the same pattern as basal eicosanoid release, suggesting that changing [K+]o influenced phospholipase A2 activity, and hence, substrate availability. At all [K+]o values, from 0 mM to 75 mM, cicletanide reduced the release of radioactivity from macrophages prelabelled with [14C]arachidonic acid (by about 15%). In the presence of [K+]o, cicletanide had a stimulatory effect on the metabolism of the free fatty acid which masked the decrease in eicosanoid release expected due to inhibition of arachidonic acid release from phospholipid. In the presence of 5 mM K+, cicletanide inhibited the basal release but enhanced the arachidonic acid-stimulated synthesis of eicosanoids from resident macrophages in a dose-related fashion, confirming the dual action of the drug, i.e., the inhibitory effect on arachidonic acid release and the stimulation of arachidonic acid metabolism. The possible in vivo significance of these results is discussed.

Arachidonic acid release by basophilic leukemia cells and macrophages stimulated by Ca2+ ionophores, antigen and diacylglycerol: essential role for protein kinase C and prevention by glucocorticosteroids.

The role of protein kinase C in phospholipase A2 (PLA2) activation in rat basophilic leukemia cells (RBL-2H3) and macrophages was investigated. 12-O-Tetradecanoyl phorbol 13-acetate (TPA) doubled ionomycin-induced PLA2 activity, assessed by [3H]arachidonate release. Protein kinase C inhibitors, staurosporine and K252a (100 nM) or H-7 (15 micrograms/ml) inhibited ionomycin-stimulation of PLA2 activity by 62, 75 and 80%, respectively. Down-regulation of protein kinase C by prolonged treatment with TPA inhibited Ca2(+)-ionophore A23187 or antigen-stimulation of [3H]arachidonate release by 80%. We examined whether the inhibitory effect of dexamethasone (DEX) on PLA2 activity is related to modulation of protein kinase C activity. The 50% inhibition by DEX of ionomycin elevation of [3H]arachidonate release was almost overcome by addition of TPA. The Ca2+ ionophore and antigen-induced increase in [3H]TPA binding to intact RBL cells was not impaired by DEX. However, DEX markedly reduced phosphorylation of several proteins. 1-Oleoyl-2-acetyl-glycerol (OAG) had a sustained stimulatory effect on PLA2 activity in isolated plasma membranes derived from treated bone-marrow intact mouse macrophages, while both DEX and staurosporine reduced elevated PLA2 activity by 68 and 84%, respectively. The results support an essential role for protein kinase C in regulation of PLA2 activity.

Activation of the murine monocyte/macrophage cell line, J774A1 by poly(A).poly(U): I. Binding of poly(A).poly(U) and induction of oligo-2',5'-adenylate synthetase.

Binding and internalization of the synthetic double-stranded complex poly(A).poly(U) were studied on a murine monocyte/macrophage cell line J774A1. Poly(A).poly(U) increased in a dose-dependent fashion the oligo-2',5'-adenylate synthetase demonstrating that those cells were responsive to this agonist. Binding of [32P]poly(A).[32P]poly(U) to the cells reached an apparent kinetic equilibrium within 4 h and was saturable (apparent Kd = 9.99 +/- 0.09.10(-2) g/l and Bmax 13.3 +/- 5.3.10(-3) g/l per 10(6) cells) and temperature-dependent. The binding of poly(A).poly(U) was competitively inhibited by various polynucleotides but not by other structurally unrelated compounds. Analysis of cell-associated [32P]poly(A).[32P]poly(U) demonstrated a minimal degradation of this polyribonucleotide over a 4-h incubation period. Autoradiography of cells incubated with [3H]poly(A).[3H]poly(U) revealed that poly(A).poly(U) was internalized and migrated to cell nuclei. These results suggest that poly(A).poly(U) is internalized in J774A1 cells via an endocytotic process.

Is there a case for PAF antagonists in the treatment of ischemic states?

It is becoming clear that PAF plays an important role in a variety of life-threatening pathologies including shock, asthma, graft rejection and ischemia-induced damage. Pierre Braquet and colleagues analyse recent reports on PAF and ischemia and propose a hypothesis based on the catastrophe theory to explain why PAF antagonists are effective in countering ischemic injury and many other disorders. PAF antagonists, perhaps in combination with other agents, may consequently prove to have extensive therapeutic potential.

Beta 2-adrenoceptor agonists regulate the IL-4-induced phenotypical changes and IgE-dependent functions in normal human monocytes.

The beta 2-adrenoceptor agonists salbutamol and fenoterol were tested for their regulatory effects on human monocyte phenotype and functions, either alone or in combination with interleukin-4 (IL-4). These drugs enhanced in a dose-dependent manner the IL-4-induced membrane and mRNA expression of the low-affinity receptor for immunoglobulin E (IgE) (CD23), as well as the release of its soluble form, sCD23. Salbutamol and fenoterol alone elicited expression of the monomorphic beta 2-chain (CD18) of the leukocyte functional antigen (LFA1) family. This effect appeared to be restricted to CD11b (CR3) and CD11c (gp 150-95), because CD11a (LFA-1 alpha chain) was not modified. beta 2-Adrenoceptor stimulation was also found to potentiate the effect of IL-4 on CD11b, CD11c, and CD18 expression. In contrast, these agents alone did not alter the level of major histocompatibility complex class II and CD14 antigens or modify their respective up- and down-regulation by IL-4. Ligation of CD23 on IL-4-preincubated (CD23+) monocytes with IgE/anti-IgE immune complexes induced the release of free radicals nitric oxide and of the proinflammatory mediators IL-6 and thromboxane B2 (TxB2). Addition of salbutamol, inactive alone, potentiated the generation of superoxide anion and of nitric oxide generation, as well as the production of IL-6 and TxB2 triggered by CD23 ligation. These results indicate that beta 2-adrenoceptor stimulation potentiates in vitro the IL-4-induced phenotypical and functional changes on monocytes and suggest that such an interaction could occur in IgE-dependent immune reactions.

Platelet-activating factor antagonists (BN 52021 and BN 50730) inhibit tumor necrosis factor-alfa-mediated cytotoxicity on murine L929 tumor cells.

Tumor necrosis factor (TNF)-alfa has been described as a mononuclear phagocyte-produced cytotoxin that causes the necrosis and regression of some tumors. The mechanism of the cytotoxicity and the basis for the differential cytotoxic effects of TNF against cells of various origin remains unclear. It has also been reported, that murine TNF stimulates the production of platelet-activating factor (PAF) by cultured peritoneal macrophages, and that PAF enhances TNF production by alveolar macrophages. Furthermore, it is known that the synthesis and release of PAF are inhibited by plasma proteinase inhibitors. This study was devoted to investigate the effects of two specific PAF antagonists (BN 52021 and 50730), and a proteinase inhibitor (aprotinin; GordoxR) on the TNF-induced cytotoxicity in L929 murine fibroblasts. Our present findings indicate that TNF-induced cytotoxicity is inhibited in a dose-dependent manner by the PAF antagonists studied and by the kallikrein inhibitor aprotinin. These findings provide further evidence suggesting that PAF might be involved in the process of the TNF-alfa-induced cytotoxicity of L929 mouse fibroblasts.

Functional interaction between beta 2-adrenoceptor agonists and interleukin-4 in the regulation of CD23 expression and release and IgE production in human.

Normal human peripheral blood mononuclear cells (PBMC) produced IgE when stimulated with IL-4. In the present report it was shown that beta 2-adrenoceptor agonists, salbutamol and fenoterol, potentiated the IL-4-induced IgE production without significantly affecting the expression of the low affinity receptor for IgE at the cell surface of monocytes and B lymphocytes. However, beta 2-adrenoceptor agonists were shown to enhance at day 7 the IL-4-induced release of the soluble form of CD23 (sCD23) by PBMC. This effect was specific since a beta-adrenoceptor antagonist, D,L-propranolol, inhibited the IL-4-induced IgE production by these cells. Alternatively, the beta 2-adrenoceptor agonists inhibited the production by these cells of interferon-gamma (IFN-gamma) but did not affect the production of IL-4 when stimulated with phytohemagglutinin A + a phorbol ester. These data suggest that beta 2-adrenoceptor agonists influence the IL-4-induced IgE production in humans by enhancing the release of sCD23 and inhibiting the production of endogenous IFN-gamma. In addition to the effect on the IL-4-induced IgE production it was shown that beta 2-adrenoceptor agonists potentiated the effect of IL-4 on a human promonocytic cell line, U 937, by enhancing CD23 expression and release and by inducing the differentiation of these cells into monocyte-like cells. Taken together, these data indicate that beta 2-adrenoceptor agonists potentiated the effect of IL-4 and that this functional interaction is different considering the cell-lineage and the stage of differentiation of these cells.

Effects of low extracellular sodium concentration on reperfusion induced arrhythmias: changes in the myocardial sodium, potassium and calcium contents in isolated guinea pig hearts.

Isolated guinea pig hearts subjected to global ischaemia were used to investigate whether low extracellular Na+ exerts an anti-arrhythmic action against reperfusion arrhythmias, and the effects of extracellular Na+ manipulation upon myocardial ion contents (Na+, K+ and Ca2+) during ischaemia and reperfusion were studied. Using an optimal concentration of 144 mmol.litre-1 of extracellular Na+, hearts were subjected to 10, 20, 25, 30 or 40 min of global ischaemia followed by 25 min reperfusion. A bell shaped curve was obtained such that with increasing durations of ischaemia from 20 to 30 min there was an increasing incidence of reperfusion arrhythmias. Beyond this optimum (at which 100% exhibited reperfusion induced ventricular fibrillation and tachycardia) there was a decline in the susceptibility of the hearts to arrhythmias. Low extracellular Na+ was given 5 min prior to the global ischaemia and maintained during reperfusion. With extracellular Na+ of 24, 54, 84 and 114 mmol.litre-1, reperfusion induced ventricular fibrillation and tachycardia were reduced from their control incidence of 91% and 100% to 8% (p less than 0.001) and 17% (p less than 0.001), 17% (p less than 0.01) and 17% (p less than 0.001), 41% (p less than 0.05) and 50% (p less than 0.05), and 91% and 91%, respectively. Both ischaemia induced Na+ gain and K+ loss were inhibited by low extracellular Na+ (24 mmol.litre-1). During reperfusion, myocardial Na+ was further increased in the control group and this value was lower in the low extracellular Na+ group. In control hearts, myocardial K+ was suddenly increased during the first 5 min of reperfusion, then continuously decreased until the end of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible involvement of platelet activating factor in anaphylaxis of passively sensitised, isolated guinea pig hearts.

There is evidence that cardiac tissue may be a target for antigen/antibody reactions. Platelet activating factor (PAF) is released during anaphylaxis and could mediate cardiac damage. To investigate this, guinea pigs were passively sensitised by anti-ovalbumin rabbit serum (6 mg.kg-1 intravenously) and 24 h later their hearts were excised and isolated according to a working heart preparation technique. After a 20 min equilibration period, anaphylactic challenge was induced by a bolus injection of ovalbumin (2 mg in 0.2 ml buffer) via the side arm of the aortic cannula. Heart rate, coronary flow, aortic flow, left ventricular developed pressure (LVDP), its first derivative (LVdp/dtmax) and left ventricular end diastolic pressure (LVEDP) were recorded. After ovalbumin challenge, heart rate and LVEDP were markedly increased, while coronary flow, aortic flow, LVDP, and LVdp/dtmax were profoundly decreased. All these alterations were over within 5 min, and the measured variables returned to approximately the pre-challenge values. BN 52021, a specific PAF receptor antagonist, was dissolved in the perfusion buffer and given in doses of 15, 30 and 60 mumol.litre-1 10 min prior to the induction of anaphylactic challenge until the end of the observation period. BN 52021 inhibited the increase in heart rate and LVEDP and the decrease in coronary and aortic flow, LVDP and LVdp/dtmax in a dose dependent manner. The changes produced by 30 and 60 mumol.litre-1 were statistically significant at the levels of p less than 0.01 and p less than 0.001 when compared to the control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of BN 50739, a new platelet activating factor antagonist, on ischaemia induced ventricular arrhythmias in isolated working rat hearts.

STUDY OBJECTIVE: The aim was to investigate the role of platelet activating factor (PAF) in myocardial ischaemia by using BN 50739, a new specific PAF receptor antagonist with a hetrazepine framework. DESIGN: Isolated working rat hearts were subjected to regional ischaemia, induced by ligation of the left main coronary artery for 30 min, followed by reperfusion. BN 50739 was applied at concentrations of 10(-7), 10(-6), 10(-5) and 5 X 10(-5) M, and its effects on the incidence of ischaemia induced and reperfusion induced ventricular tachycardia and ventricular fibrillation and heart functions, such as heart rate, coronary flow, aortic flow, left ventricular developed pressure (LVDP), its first derivative (LVdP/dtmax), and left ventricular end diastolic pressure (LVEDP), were determined. EXPERIMENTAL MATERIAL: Studies were performed on isolated working hearts of male Sprague-Dawley rats weighing 300-360 g. Hearts were perfused with BN 50739 dissolved in dimethylsulphoxide. Control hearts were perfused with the vehicle. MEASUREMENTS AND MAIN RESULTS: Regional ischaemia triggered ventricular arrhythmias showing high incidence between 12 and 20 min with peak appearance at 16 min. BN 50739 induced dose dependent protection against ventricular tachycardia and fibrillation: incidences declined from their respective control values of 91% and 75% to 33% (p less than 0.05) and 8% (p less than 0.05) after exposure to 10(-5) M, and to 25% (p less than 0.05) and 8% (p less than 0.05) after exposure to 5 X 10(-5) M concentrations. Reperfusion of the ischaemic myocardium resulted in an immediate appearance of ventricular tachycardia and fibrillation, but these were not suppressed by the PAF antagonist. Regional ischaemia slightly reduced heart rate, markedly decreased coronary flow, aortic flow, LVDP and LVdP/dtmax, and increased LVEDP. With the exception of LVEDP, these variables were not influenced by the drug. BN 50739, applied at a concentration of 5 X 10(-5) M, reduced LVEDP significantly during the whole ischaemic period. CONCLUSIONS: Under in vitro conditions PAF is likely to be involved in the genesis of ischaemia induced ventricular arrhythmias since BN 50739, a specific PAF receptor antagonist, exerts a protective effect against these rhythm disturbances. This suggests that PAF antagonists may have benefit in the clinical management of acute myocardial ischaemia.

Pharmacologic modulation of picryl chloride-induced contact dermatitis in the mouse.

A biphasic response of ear swelling was observed 2 h and 24 h after application of the antigen to picryl chloride-sensitized Balb/c mice. A platelet-activating factor (PAF) antagonist, BN 52063, or the anti-inflammatory drug, betamethasone, applied topically or injected subcutaneously, inhibited in a dose-dependent fashion the antigen-induced increase in ear thickness observed after 24 h. In addition, BN 52063 and betamethasone presented a synergistic effect when administered in vivo simultaneously and subcutaneously. Indomethacin administered subcutaneously at the time of the antigen challenge significantly potentiated the early swelling phase and inhibited the late one. In contrast, the inhibitors of histamine and serotonin, ketotifen and methysergide, respectively, modulated mostly the early, and to a lower extent the late phase when administered at the time of antigen challenge. In contrast, none of these drugs inhibited the late phase reaction when administered 4 h after the antigen. A significant eosinophil and mononuclear-cell ear infiltrate was observed following topical application of the antigen, a phenomenon that was markedly reduced by either BN 52063 or betamethasone. These results demonstrate the effectiveness of PAF antagonists, either alone or in association with glucocorticosteroids, in experimental CD, the modulation of the infiltration of eosinophils and mononuclear cells possibly explaining part of the inhibitory action of these drugs.

Endothelin stimulates steroid secretion by frog adrenal gland in vitro: evidence for the involvement of prostaglandins and extracellular calcium in the mechanism of actin of endothelin.

Endothelin (ET-1) is a pleiotropic regulatory peptide which exerts multiple endocrine actions on the cardiovascular system. In the present study, we have investigated the possible role of ET-1 in the regulation of adrenocortical cells using perifused frog interrenal (adrenal) slices. Graded doses of ET-1 from 10(-11)-10(-9) M stimulated both corticosterone and aldosterone production in a dose-dependent manner. Repeated 20-min pulses of ET-1 (10(-9) M), given at the frequency of one pulse per 90 min, resulted in a marked reduction of the secretory response after the second pulse. Prolonged administration (3 h) of ET-1 induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline of corticosteroid secretion. Perifusion of frog adrenal tissue with ET-1 (10(-9) M) caused a significant increase in the release of prostaglandin E2 (PGE2) and 6-keto-PGF1 alpha, the stable metabolite of the prostacyclin PGI2. The enhancement of PG biosynthesis preceded by 10 min the peak of corticosteroids. When repeated pulses of ET-1 were administered, a significant diminution of the production of PGE2 and 6-keto-PGF1 alpha was observed after the second pulse. The cyclooxygenase inhibitor indomethacin (5 microM) totally suppressed the stimulatory effect of ET-1 on corticosterone and aldosterone secretion; in contrast, indomethacin did not affect ACTH-evoked corticosteroid secretion. Perifusion of adrenal slices with a calcium-free solution or addition of cobalt (4 mM) induced total inhibition of the stimulatory effect of ET-1. These results demonstrate that ET-1 is a potent stimulator of corticosterone and aldosterone secretion from frog adrenal gland in vitro. Our data show that repeated or prolonged administration of ET-1 induces a rapid desensitization phenomenon. The data also indicate that ET-1-evoked corticosteroid secretion is mediated by an increase in PG biosynthesis and requires the presence of extracellular calcium.