Acute bronchial obstruction following inhalation of PAF in asthmatic and normal subjects: comparison with methacholine

Platelet-activating factor (PAF) may play a role in the pathophysiology of asthma but controversies exist about bronchial responsiveness toward this mediator in asthma. We have compared the variations in the specific conductance (sGaw) and forced expiratory volume in one second (FEV1) in 12 asthmatics and 12 normal subjects after inhalation of doubling doses of PAF (15-120 micrograms) and methacholine (18 to at least 144 micrograms). In order to take into account a possible tachyphylaxis, we compared PAF dose-response curves performed on one day with the curves obtained by giving the same doses separately on different days. Repeated inhalations of doubling doses of PAF caused sGaw and FEV1 to plateau after the second dose in each group, whereas methacholine provoked a dose-related decrease in sGaw and FEV1. A dose-dependent decrease in the functional indices was restored when the different doses of PAF were administered on separate days. In both groups, the fall in sGaw after inhalation of 60 micrograms as a single dose was higher than that achieved when this dose was given during a full bronchial challenge. The falls in sGaw and FEV1 after PAF inhalation were significantly higher in the asthmatics than in the normal subjects. The provocative dose of PAF causing a 35% fall in sGaw (PD35,sGaw) PAF was only twofold lower in the asthmatics than in the normal subjects (p < 0.05), while it was 11 fold lower for methacholine (p < 0.001). When the PD35,sGaw values were compared, PAF was found on a molar basis to be 33 fold more potent than methacholine in the normal subjects, but only fivefold more potent in the asthmatics (p < 0.05). The percentage falls in FEV1 (calculated by interpolation) for a 35% fall in sGaw, were greater in asthmatics than in normals both for methacholine (p < 0.05) and PAF (p = 0.09). Our results demonstrate a tachyphylaxis after inhalation of platelet-activating factor in normal subjects and asthmatics, and show that asthmatics develop a greater bronchial obstruction than normal subjects even if methacholine is more sensitive than platelet-activating factor at discriminating between the two groups.

Isolation, chemical characterization, and subcellular distribution of 1-O-alkyl-2-acetyl-sn-glycerol in Tetrahymena pyriformis cells

1-O-Hexadecyl-2-acetyl-sn-glycerol, the immediate precursor of platelet- activating factor (PAF) in its de novo formation, was detected in the protozoon Tetrahymena pyriformis. It was purified from the total lipid extract by TLC, after successive developments in two different solvent systems. Characterization was assessed by (a) gas-liquid chromatography with electron capture detection, and (b) gas chromatography combined with mass spectrometry in selected ion monitoring mode, after derivatization with heptafluorobutyric acid anhydride and tert-butyldimethylchlorosilane/imidazole, respectively. Its quantity was found to be 0.1 nmol/10(7) cells from the GC-MS, using authentic alkylacetylglycerol as external standard. Cell fractionation revealed that alkylacetylglycerol is located exclusively in the microsomal fraction of the protozoon. Previously, we have reported the occurrence of PAF in the microsomal fraction, as well as a dithiothreitol-insensitive CDP-choline: cholinephosphotransferase activity that utilizes exogenous alkylacetylglycerol as substrate in the mitochondrial and microsomal fractions. The above findings indicate that PAF can be formed in the cell by the de novo pathway.

Comparison of PAF- and fMLP-induced [Ca2+]i transients in human polymorphonuclear leukocytes

Changes of [Ca2+]i in human polymorphonuclear leukocytes (PMNL) were studied. PMNL suspension was activated three times every 5 min with 10(-7) M PAF and fMLP. Both PAF and fMLP, induced three consecutive [Ca2+]i transients in PMNL suspended in medium with 1 mM Ca2+. The first Ca2+ response was a result of Ca2+ release from internal stores and the extracellular Ca2+ influx, while the second and third responses were completely dependent on Ca2+ influx from extracellular space. The contribution of Ca2+ from intracellular stores to the first PAF-induced Ca2+ response was about 1.4-fold lower in comparison with the first fMLP induced Ca2+ response (27 +/- 1 vs 37 +/- 6% (p < 0.05). Previous addition of PAF enhanced 3-fold (p < 0.001) the PMNL response to fMLP while cells pretreated with fMLP failed to increase their [Ca2+]i after challenge with PAF. PMNL from 40% of donors did not respond to PAF in the presence of 100 nM Ca2+. However, the cells responding to PAF as the cells treated with fMLP or cyclopiazonic acid released almost the entire Ca2+ from intracellular stores after challenge. Subtraction of mean [Ca2+]i transients in the presence of 100 nM Ca2+ from that obtained in medium with 1 mM Ca2+ showed that, in PMNL stimulated with PAF in contrast to the cells treated with fMLP, the onset of Ca2+ influx from extracellular space precedes Ca2+ release from intracellular stores. These results suggest that PAF-induced Ca2+ influx from extracellular space is at least partly independent of Ca2+ release from intracellular stores.

Platelet-activating factor and leukotrienes in acute otitis media, secretory otitis media, and chronic otitis media on the acute excerbation

The present study was carried out for the purpose of measuring platelet activating factor (PAF) and leukotrienes (LTs) in middle ear fluid (MEF) or in otorrhea of children with acute otitis media (AOM), with secretory otitis media (SOM), and with chronic otitis media (COM) on the acute exacerbation. PAF, LTC4, and LTD4+LTE4 concentrations were measured by radioimmunoassay in purulent MEFs obtained from 15 ears of 15 children with AOM, in mucoid or gluey MEFs from 16 ears of 15 children with SOM, and in purulent otorrhea from 9 ears of 9 children with COM on the acute exacerbation. PAF concentrations were 25.4 +/- 9.0 ng/mg total phospholipid (TPL) in AOM, 4.9 +/- 1.9 ng/mg TPL in SOM, 20.7 +/- 15.7 ng/mg TPL in COM, demonstrating significant differences between AOM and SOM (p < 0.05) and between COM and SOM (p < 0.01). LTC4 concentrations were 92.9 +/- 73.8 pg/mg total protein (TP) in AOM, 52.0 +/- 42.5 pg/mg TP in SOM, and 28.5 +/- 11.2 pg/mg TP in COM. LTD4+LTE4 concentrations were 326.5 +/- 177.0 pg/mg TP in AOM, 288.2 +/- 144.6 pg/mg TP in SOM, and 94.0 +/- 58.1 pg/mg TP in COM, demonstrating significant differences between AOM and COM and between SOM and COM (p < 0.01). The results obtained indicated that PAF was involved in the onset of AOM and COM on the acute exacerbation, and that LTs played an important role in SOM.

Effects of H1- and H2-antihistamines on platelet-activating factor and bradykinin-induced inflammatory responses in human skin

Previous studies show that oral antihistamines affect the weal and flare response to intradermal injections of the inflammatory mediators platelet-activating factor (PAF) and bradykinin (BK). The aim of this study was to compare the effects of terfenadine (an H1-antagonist) and cimetidine (an H2-antagonist) on weal and flare responses to PAF and BK in healthy non-atopic human volunteers. The effects of doxepin on PAF responses were investigated, as there is evidence that doxepin may have direct anti-PAF effects in addition to its known antihistaminic actions. Terfenadine significantly reduced weal and flare responses to PAF (mean reduction 53 and 73%, respectively) and flare responses to BK (mean reduction 78%) but had no effect on weal responses to BK. Doxepin significantly reduced both weal and flare responses to PAF (mean reduction 43 and 68%, respectively, at higher doses of PAF). Cimetidine had no effect on weal or flare responses to PAF or BK. These findings suggest that the flare response to intradermal BK is mediated via histamine release while the weal response is not. The effects of the various antagonists of PAF-induced responses suggest that its effects too may be mediated via histamine, the similarity of the effects of terfenadine and doxepin on these responses indicating that the effects of doxepin may be due to its known antihistamine activity rather than to any specific PAF-antagonistic properties. Platelet-activating factor (PAF) is a phospholipid which is released from a wide range of cell types and also from vascular endothelium. PAF is formed by the conversion of ether-linked phospholipids initially to the biologically inactive lyso-PAF and then by acetylation to PAF. Intradermal injection of PAF in human skin causes vasodilatation and increased vascular permeability, producing a weal and flare response with accompanying pruritus. Bradykinin (BK) is a vasoactive polypeptide formed by the action of enzymes known as kallikreins on inactive precursors called kininogens. Its effects include an increase in blood flow and vascular permeability and stimulation of the release of prostaglandins and histamine. On intradermal injection in human skin it causes a weal and flare response with associated pain rather than pruritus. Previous studies have suggested that the weal and flare response to PAF may be mediated in part by histamine release. Given that BK is known to cause histamine release it appears possible that the responses to both compounds may be modified by conventional antihistamines. Experiments based on this premise have found that antihistamines have a pronounced effect on the flare response to PAF but a less marked effect on weal responses. The weal response to BK was unaffected by systemic antihistamines but studies have produced conflicting results with regard to effects on the flare response. The aim of this study was to compare the effects of terfenadine (an H1-antagonist) and cimetidine (an H2-antagonist) on PAF- and BK-induced weal and flare responses in healthy, non-atopic human volunteers. Based on the treatment of cold urticaria it has been suggested that doxepin, which has known H1- and H2-antagonistic effects, may in addition show specific anti-PAF activity. We compared the effects of doxepin on PAF-induced intradermal responses with those of terfenadine and cimetidine in this study.

The modulatory effect of antigen- and PAF-induced asthmatic reaction by aerosol administration of OKY-046 in guinea pigs

The therapeutic effect of a thromboxane A2 (TXA2) synthetase inhibitor on asthma is still controversial. This study was aimed at clarifying its effect on asthmatic reactions in guinea pigs. Both ovalbumin (OVA)- and platelet activating factor (PAF)-induced dual phase airway spasm and hyperreactivity in guinea pigs were used as the asthma model. Our results demonstrated that aerosol administration of OKY-046 could inhibit both OVA- and PAF-induced late phase bronchoconstriction and airway hyperreactivity to methacholine in OVA sensitized guinea pigs. PAF administration could also induced dual phase bronchoconstriction in normal guinea pigs. Similarly, late phase airway spasm and airway hyperreactivity after PAF exposure was also blocked by OKY-046. In conclusion, aerosol administration of OKY-046 is a safe and effective way to modulate OVA- and PAF-induced asthmatic reactions. The protective effect of OKY-046 on OVA- and PAF-induced late phase bronchoconstriction and airway hyperreactivity indicates that TXA2 might play an important role in the late phase asthmatic reaction and airway hyperreactivity. The normalization of PAF-induced airway hyperreactivity by OKY-046 also indicates that PAF induced airway inflammation might be through the generation of TXA2.

[Effect of KW-4679, a novel antiallergic drug, on platelet-activating factor (PAF)-induced bronchoconstriction, airway hyperresponsiveness and pulmonary cell accumulation in guinea pigs]

We assessed the effects of KW-4679 on bronchoconstriction, airway hyperresponsiveness and infiltration of inflammatory cells into the bronchoalveolar lavage (BAL) fluid induced by platelet-activating factor (PAF) in guinea pigs. (1) KW-4679 (1, 10 mg/kg, p.o.) significantly inhibited PAF-induced bronchoconstriction in anesthetized, ventilated guinea pigs. Ketotifen (1, 10 mg/kg, p.o.) also significantly inhibited that reaction. (2) Intravenous administration of PAF (600 ng/kg/hr) to ventilated anesthetized guinea pigs induced bronchial hyperresponsiveness to histamine or substance P. PAF-induced bronchial hyperresponsiveness was significantly attenuated by pretreatment with KW-4679 (3 mg/kg, i.v.). (3) Exposure of guinea pigs to an aerosol of PAF induced an increase in the numbers of total leukocytes, eosinophils, neutrophils and lymphocytes in BAL fluid at 24 hr. KW-4679 (10 mg/kg, p.o.) reduced the increase in eosinophils in BAL fluid. Ketotifen (10 mg/kg, p.o.) partially reduced the increase in eosinophils in BAL fluid. (4) KW-4679 did not inhibit PAF-induced rabbit platelet aggregation. These observations indicate that KW-4679 attenuates the PAF-induced pulmonary reactions in guinea pigs and that these actions may be beneficial for the treatment of allergic bronchial asthma.

Streptococcus pneumoniae anchor to activated human cells by the receptor for platelet-activating factor

The Gram-positive bacterium Streptococcus pneumoniae is a major cause of pneumonia, sepsis and meningitis. Although the invasive disease is severe, some 40% of individuals harbour the pneumococcus in the nasopharynx asymptomatically. Here we investigate the molecular elements of the encounter between host and pathogen that distinguish these different outcomes. We show that inflammatory activation of human cells shifts the targeting of the pneumococcus to a new receptor, that for the G-protein-coupled platelet-activating factor (PAF). Only virulent pneumococci engage the PAF receptor. Attachment of the bacterial phosphorylcholine to the PAF receptor enhanced adherence, which was coupled to invasion of endothelial, epithelial and PAF-receptor-transfected cells. This progression could be arrested in vitro and in vivo by PAF-receptor-specific antagonists, suggesting a possible approach to therapy.

Differences in eosinophil and neutrophil chemotactic responses in sowda and generalized form of onchocerciasis

Extravasation of host's leukocytes from blood vessels into inflammatory tissues represents a prerequisite for a subsequent interaction with invaded parasites. The migratory responses of eosinophilic and neutrophilic granulocytes in the polar forms of the filarial infection onchocerciasis were investigated. The hyporeactive, generalized form, the chronic hyperreactive (sowda) form and persons without signs of onchocerciasis from a hypoendemic area for onchocerciasis were compared. Eosinophils from sowda patients responded more strongly to the inflammatory mediator platelet-activating factor (PAF) than those from generalized patients and persons without onchocerciasis. The most significant differences were found between the sowda group and a subgroup of the generalized form with 16-80 microfilariae/mg skin (P<0.05) while patients with low microfilarial density exhibited chemotactic responses similar to the sowda group. In contrast to the strong eosinophil response, neutrophils from sowda patients appeared unreactive to PAF and the tripeptide activator formyl-methionyl-leucyl-phenylalanine (fMLP), thereby differing from both other groups. Laboratory data confirmed a state of hyperreactivity in sowda patients similarly found in generalized patients with low microfilarial density and contrasting with those with a microfilarial density of 16-80 mf/mg. The results revealed an inverse chemotactic responsiveness of eosinophil and neutrophil granulocytes in sowda patients and strengthened the observation of a spectrum of host's responsiveness in onchocerciasis.

[Inhalation of platelet-activating factor induced guinea pig airway hyperresponsiveness: role of eosinophils activation]

Exposure of guinea pigs to aerosols of 200 micrograms/ml platelet-activating factor 24 h later, airway hyperresponsiveness to histamine induced and number of eosinophils and hypodense eosinophils in bronchoalveolar lavage fluid (BALF) increased, comparing with the control group. The number of eosinophils in BALF was corelated with PC20 value in PAF-treated group (r = -0.62, P < 0.05). However, the percentage of hypodense eosinophil in BALF had closer relation to airway responsiveness (r = -0.84, P < 0.01). The content of peroxidase in hypodense eosinophils in BALF for guinea pigs treated by inhalation of PAF was lowered markedly than that in normodense eosinophil (P < 0.05). The result suggested that chemotaxis and activation of eosinophils by PAF might play an important role in airway hyperresponsiveness.

Protective effect of propionyl-L-carnitine against PAF-induced rat paw oedema

Recent reports from our laboratory gave evidence showing that propionyl-L-carnitine (PLC), unlike L-carnitine (LC) and acetyl-L-carnitine (ALC), has anti-inflammatory activity in some models of vascular inflammation in rodents. The present paper shows that PLC (50 to 200 mg kg-1 i.p.) inhibits rat paw oedema induced by platelet activating factor (PAF), while LC and ALC, as well as indomethacin and phenylbutazone, are ineffective. The extent of the maximal inhibition produced by PLC at 200 mg kg-1 was comparable to that of betamethasone 0.05 mg kg-1 or sodium salicylate 100 mg kg-1. PLC inhibited also the early phase (1-2 h) of carrageenin-induced rat paw oedema, which is partly dependent on PAF release, but it was ineffective in the eicosanoid-dependent late phase (3-4 h) of the carrageenin oedema. We suggest that such anti-inflammatory activity of PLC may be due to various mechanisms converging on a stabilizing action upon biomembranes.

Platelet activation by platelet aggregation factor from Eisenia foelide

A platelet activating factor from earthworm, Eisenia foelide (EPAF, 25.9 mumol.L-1), induced human platelet aggregation and 5-HT (maximal release of 89% at EPAF 74.1 mumol.L-1) was detected during this process. Neither creatine phosphate/creatine phosphate kinase (CP/CPK) nor aspirin completely inhibited the EPAF-induced platelet aggregation. In the presence of fibrinogen, EPAF (55.6 mumol.L-1) induced the aggregation of human platelet which had been thrombin-treated and degranulated. Results indicated that EPAF was a potent platelet agonist and the EPAF-induced platelet aggregation was ADP- and TXA2-independent.

Protective effects of papaverine salicylate in mouse ear dermatitis and PAF-induced rat paw oedema

Papaverine salicylate (MR-800) has been tested as a topical antiinflammatory agent in several models of skin inflammation in rodents, such as mouse ear dermatitis induced by croton oil, cantharidin or zymosan, and rat paw oedema induced by PAF. MR-800 exerted a dose-dependent inhibitory activity in all assays, when equimolar doses of sodium salicylate or papaverine were less effective, suggesting the existence of a favourable synergism between salicylate and papaverine.

Maintenance of high risk pregnancies: role of prostaglandins and other mediators

The initiation of a complex cascade of events resulting in the delivery of a healthy newborn appears to involve the integrated actions of the fetus, mother and the placenta. Many putative factors have already been extensively reviewed. Instead of concentrating on the action of estrogen and progesterone, the role of regulators of myometrial activity such as prostaglandins as well as the fetal pituitary-adrenal system, oxytocin, corticosteroids, leukotrienes, platelet activating factor, endotoxin and cytokines to name a few, will be discussed. Nevertheless, there is an increasing weight of evidence suggesting that many of the above agonists converge upon a final pathway of prostaglandin production which subsequently increases myometrial responsiveness. Prostaglandins are involved at levels of myometrial regulation such as myometrial gap junction formation, intracellular calcium flux modulation, synchronisation of myometrial contraction via interaction with oxytocin thus having stimulatory effects on uterine contractility, as well as cervical maturation (via PGE2). Importantly, there has been clinical benefit of a more thorough understanding of the physiology of myometrial regulation at the time of partuition. The approach to the treatment of preterm delivery has improved, eventhough the exact mechanism(s) and cause(s) of this phenomenon remain an enigma. Current tocolytic therapy is not generally prophylactic but commences after labour, contractions and cervical dilatation are underway. Key regulatory pathways have been pin-pointed that present opportunity for tocolysis including:-c-AMP inhibition of contraction by beta-mimetic agents, inhibition of calmodulin-calcium function, inhibition of calcium influx by calcium channel blockers, inhibition of prostaglandin production, modulation of myometrial function by peptide hormones or antagonists (e.g. relaxin, VIP and oxytocin antagonists).(ABSTRACT TRUNCATED AT 250 WORDS)

Pentoxifylline attenuates platelet activating factor-induced permeable edema in isolated perfused guinea pig lungs

The effect of pentoxifylline (Pen) on platelet activating factor (PAF)-induced pulmonary injury was studied in isolated guinea pig lungs perfused with cell-free Tris buffered Ringer solution. PAF (1.0 nmol.L-1) increased lung weight and pulmonary filtration coefficient (Kf), which indicated the formation of high permeable pulmonary edema. Pen (0.5 and 1.0 mmol.L-1) markedly attenuated the PAF-induced increment of lung weight and vascular permeability, but not the increment of pulmonary capillary pressure and venous resistance. There was no correlation between the severity of lung edema and the number of leukocytes in the perfusates. These results suggest that Pen has direct anti-permeability effect on pulmonary microvessels.

Effect of E-type prostaglandins on bradykinin-induced plasma extravasation in the knee joint of the rat

We studied the effect of different E-type prostaglandins on an experimental model of inflammation in the rat. Plasma extravasation was induced in the knee joint of the rat by continuous perfusion of two potent inflammatory mediators, bradykinin (160 nM) or platelet activating factor. Both prostaglandin E1 and prostaglandin E2 (0.5-500 ng ml-1), when perfused with bradykinin, produced a similar dose-dependent enhancement of plasma extravasation. Prostaglandin E2 (0.5-500 ng ml-1) also dose dependently enhanced plasma extravasation induced by platelet activating factor, while prostaglandin E1 significantly enhanced platelet activating factor-induced plasma extravasation only at concentrations above 5 ng ml-1. In contrast, co-perfusion of bradykinin or platelet activating factor with the prostaglandin E1 analogues, enisoprost and misoprostol (0.5-500 ng ml-1) did not enhance plasma extravasation. In fact, misoprostol attenuated plasma extravasation induced by bradykinin. These results demonstrate that in the rat knee joint, misoprostol and enisoprost have different pharmacological actions compared to their parent compound, prostaglandin E1 and to prostaglandin E2.

Heparin prevents antigen-induced airway hyperresponsiveness: interference with IP3-mediated mast cell degranulation?

We hypothesized that heparin, because of its antiallergic and/or anti-inflammatory properties, modifies airway hyperresponsiveness (AHR). We studied the effects of inhaled heparin on AHR induced by specific antigen or by platelet-activating factor (PAF), a proinflammatory mediator. Specific lung resistance (sRL) was measured in 17 allergic sheep before, immediately after, and serially for up to 2 h after airway challenge with either specific antigen or PAF. Airway responsiveness was expressed as the cumulative provocative dose of carbachol that increased sRL to 4 cmH2O/s [PD4, in breath units (BU; 1 BU = 1 breath of 1% carbachol solution)]. PD4 was determined on a baseline day and on various experimental days 2 h after airway challenge with antigen or PAF, without or after pretreatment with inhaled heparin (1,000 U/kg). Pretreatment with inhaled heparin prevented antigen-induced bronchoconstriction and postantigen AHR. PD4 was 26 +/- 2.6 (SE), 12 +/- 1.7, and 22 +/- 2.8 BU on baseline, antigen control, and postheparin days, respectively. Heparin given immediately after the antigen challenge failed to modify the magnitude and/or duration of antigen-induced bronchoconstrictor response or postantigen AHR. Heparin also failed to prevent PAF-induced changes in sRL and AHR. In vitro heparin inhibited anti-immunoglobin E- and 1,4,5-inositol triphosphate-mediated degranulation of rat peritoneal mast cells without attenuating the effects of the Ca2+ ionophore A-23187. These data suggest that in "acute responders" heparin prevents antigen-induced bronchoconstriction and AHR, possibly by inhibiting 1,4,5-inositol triphosphate-dependent mast cell mediator release and not by its anti-inflammatory action.

An optoelectronic registration method as applied to PAF-mediated hydrogen peroxide induced arterial thrombosis

In the present paper, a standardized method for the induction and registration of platelet thrombi in arterioles (500 microns diameter) of small laboratory animals is described in full detail. Using an optoelectronic analogue computer device, different discriminating parameters characteristic for the thrombotic phenomenon are presented. As the topical application of exogenous PAF-acether induces the generation of endogenous PAF-acether according to previous investigations (Bourgain et al. (1985) Prostaglandins 30, 185) it was deemed interesting to investigate the effect of hydrogen peroxide using the described methodology. It was found that the latter substance not only primes the effect of PAF-acether-induced thrombosis, but also can trigger by itself PAF-acether modulated arterial thrombus formation. Experimental evidence is adduced that these thrombotic phenomena can be most efficiently down regulated by specific PAF-acether antagonists.

Intestinal ischemia in the newborn: the role of intestinal maturation

Premature infants are susceptible to intestinal ischemia during the newborn period when their intestinal tracts are functionally and structurally immature. Studies have shown that exogenous glucocorticoids hasten intestinal maturation. We investigated the effects of hydrocortisone on platelet activating factor (PAF)-induced intestinal ischemia in the neonatal rat. On Postnatal Days 7-11, Sprague-Dawley rats were given intraperitoneal (ip) injections of either saline (SAL) or hydrocortisone (HC; 50 mg/kg total). On Day 12, rats were injected with either PAF (2 micrograms/kg) or an equal volume of saline. After 2 hr the rats were sacrificed and sections were taken for histology. The remaining intestine was analyzed for maltase, lactase, myeloperoxidase (MPO), and xanthine oxidase (XO). Experimental groups were as follows: SAL (N = 8), received saline only; SAL+PAF (N = 8), received saline plus PAF; HC (N = 3), received hydrocortisone+saline; and HC+PAF (N = 5), received hydrocortisone plus PAF. XO was significantly decreased (P < 0.001) in the hydrocortisone-treated groups (HC + SAL = 16.36 +/- 18.42 units/g protein, HC + PAF = 17.33 +/- 9.06 units/g protein) vs the controls (SAL only = 108.90 +/- 20.24 units g/protein, SAL + PAF = 145.77 21.28 units/g protein). MPO was not significantly elevated in SAL + PAF (4.60 +/- 0.95 units/g protein) vs HC + PAF (2.18 +/- 0.80 units/g protein) in this study. Maltase was significantly elevated (P < 0.001) in the HC + PAF (241.46 +/- 40.6 mole/min/g protein) and HC + SAL (152.78 +/- 16.35 mole/min/g protein) vs saline only (28.35 +/- 5.77 mole/min/g protein and SAL + PAF (37.29 +/- 8.70 mole/min/g protein. Animals (7/8) in the SAL + PAF group developed ischemia by inspection and histologic exam.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor necrosis factor-alpha mediates endotoxin-induced lung injury in platelet activating factor-primed rats

We have reported recently that lipopolysaccharide endotoxin and platelet activating factor cooperate in priming relationships to elicit lung microvascular injury. Lung injury was associated with elevated serum levels of tumor necrosis factor-alpha (TNF alpha) and histological findings highly reminiscent of the adult respiratory distress syndrome. The present study was designed to examine the role of TNF alpha in lipopolysaccharide/platelet activating factor-induced lung injury by utilizing a highly specific monoclonal antibody which block TNF alpha actions (anti-TNF alpha monoclonal antibody). Pretreatment with anti-TNF alpha monoclonal antibody (2.5-25 mg/kg i.v., n = 5-9) dose-dependently prevented the lipopolysaccharide/platelet activating factor-induced histopathological changes, lung edema (P < .01), lung myeloperoxidase activity (P < .01), elevation of neutrophil count in bronchoalveolar lavage fluid (P < .01) and increased serum thromboxane B2 (P < .01). Indomethacin (6 mg/kg i.v., n = 5) failed to modify the lung injury despite complete inhibition of thromboxane B2 formation (P < .05). These data suggest that TNF alpha might play a key role in initiation of the early inflammatory changes which lead to adult respiratory distress syndrome.

Effect of fepradinol on rat hind paw oedema induced by several inflammatory agents

Fepradinol is an effective non-steroidal anti-inflammatory agent. The effect on rat paw oedema induced by various phlogistic agents was investigated. The inhibitory effect of fepradinol (25 mg kg-1, p.o.) on dextran-induced oedema was nearly equal to that of cyproheptadine (10 mg kg-1, p.o.). On oedema induced by platelet-activating factor only fepradinol (25 mg kg-1, p.o.) and phenidone (100 mg kg-1, p.o.) clearly inhibited the inflammatory process. Both the above induced oedemas are thought to be unrelated to prostaglandins in the rat system and therefore, the anti-inflammatory activity against them is not shared by selective cyclo-oxygenase inhibitors. Fepradinol (25 mg kg-1, p.o.) displayed an inhibitory effect on the early and late stage of kaolin- and nystatin-induced oedemas in contrast with indomethacin (10 mg kg-1, p.o.) and piroxicam (10 mg kg-1, p.o.) which only inhibited the late stage. The results obtained in this study confirm that fepradinol is a potent anti-inflammatory agent and indicate that its mechanism of action is different from that of other anti-inflammatory compounds.

Anti-platelet and anti-thrombotic effects of OP-41483.alpha-CD, a prostacyclin analogue, in experimental animals

The effects of OP-41483.alpha-CD, 5(E)-6,9-deoxa-6,9 alpha-methylene-15-cyclopentyl-16,17,18,19,20-pentanor prostacyclin (PGI2).alpha-cyclodextrin clathrate, on platelet function and experimental thrombosis were studied. In human platelets, OP-41483 inhibited aggregation induced by adenosine diphosphate (ADP) or collagen, promoted disaggregation, and elevated cyclic adenosine monophosphate (cAMP) levels in vitro at the same order of concentrations. The equipotent antiaggregatory activity of OP-41483 to human platelets was observed in monkey platelets in vitro. Furthermore, intravenous administration of OP-41483 to monkeys, unlike PGI2, showed the antiaggregatory effect on platelets but with less effect on blood pressure, suggesting that a differential sensitivity to OP-41483 between platelet function and vascular tone exists in monkeys. In rabbits, OP-41483.alpha-CD attenuated platelet aggregation induced by ADP, collagen and platelet activating factor (PAF), decreased circulating platelet aggregates, and inhibited platelet adhesiveness to de-endothelialized blood vessels. These results suggest that the anti-thrombotic effects of OP-41483 are associated with its potent antiplatelet activities mainly because of the elevation of cAMP levels in the platelets. The potent anti-thrombotic and less hypotensive effects of this compound may be useful for various thrombotic disorders.

Effect of a novel xanthine derivative on experimental ulcers in rats

The effects of the novel xanthine derivative 3-ethyl-1-(6-hydroxy-6-methylheptyl)-7-propylxanthine (A90 6119, CAS 134072-58-5) on various experimentally induced ulcers was investigated in rats. A90 6119 produced a dose-dependent inhibition of gastric ulcers induced by water immersion stress and absolute ethanol with ED50- values of 2.4 and 2.8 mg/kg, p.o., respectively. The erosion induced by oral administration of 1.5% NH4OH (3 ml/rat) was significantly reduced by A90 6119 at 10 and 30 mg/kg, p.o. Likewise, A90 6119 caused a dose-dependent inhibition of gastric erosions and intestinal hemorrhage induced by platelet activating factor (PAF) with ED50- values of 8.7 and 11.9 mg/kg p.o., respectively. Duodenal ulcer induced by cysteamine was also dose-dependently inhibited by A90 6119 with an ED50-value of 0.3 mg/kg, i.p. When doses of cimetidine (200 mg/kg) and A90 6119 (10 mg/kg), equipotent in the water immersion stress model, were orally given twice daily for 5 consecutive days before the induction of gastric ulcers by stress, the H2-receptor antagonist aggravated significantly the ulcer formation while the xanthine derivative did not show such an effect. These data suggest that the 3-ethylxanthine A90 6119 possesses pronounced anti-ulcer activity and that its repeated administration might not aggravate ulcer formation and might reduce the incidence of recurrence.