Guinea Pig Lung Research Articles

Progressive pulmonary tuberculosis is not due to increasing numbers of viable bacilli in rabbits, mice and guinea pigs, but is due to a continuous host response to mycobacterial products

Tuberculosis (TB) kills more people in the world today than any other infectious disease. A better vaccine to prevent clinical tuberculosis is greatly needed. Candidate vaccines are often evaluated by infecting rabbits, mice and guinea pigs by an aerosol of virulent tubercle bacilli and culturing their lungs for viable bacilli at various times thereafter. In all three species, however, the number of viable bacilli usually does not continuously increase until the host succumbs. The number of viable bacilli increases logarithmically for only about 3 weeks. Then, the host develops delayed-type hypersensitivity (DTH) and cell-mediated immunity (CMI), which keep the number of viable bacilli rather constant during the subsequent weeks. In the immunized host, DTH and CMI stop the logarithmic increase sooner than in the unimmunized controls, so that the stationary bacillary levels that follow are lower. This review analyzes host-parasite interactions in the lungs of rabbits, mice and guinea pigs. All three species cannot prevent inhaled fully virulent tubercle bacilli from establishing an infection, but they differ markedly in the type of the disease produced once it is established.

A comparison of the molecular species compositions of mammalian lung surfactant phospholipids

While dipalmitoyl phosphatidylcholine (PC16:0/16:0) is essential for pulmonary surfactant function, roles for other individual molecular species of surfactant phospholipids have not been established. If any phospholipid species other than PC16:0/16:0 is important for surfactant function, then it may be conserved across animal species. Consequently, we have quantified, by electrospray ionisation mass spectrometry, molecular species compositions of phosphatidylcholine (PC), phosphatidylglycerol (PG) and phosphatidylinositol (PI) in surfactants from human, rabbit, rat and guinea pig lungs. While PC compositions displayed only relatively minor variations across the animal species studied, there were wide variations of PG and PI concentrations and compositions. Human surfactant PG and PI were enriched in the same three monounsaturated species (PG16:0/18:1, PG18:1/18:1 and PG18:0/18:1) with minimal amounts of PG16:0/16:0 or polyunsaturated species, while all animal surfactant PG contained increased concentrations of PG16:0/16:0 and PG16:0/18:2. Animal surfactant PIs were essentially monounsaturated except for a high content of PI18:0/20:4 (29%) in the rat. As these four surfactants all maintain appropriate lung function of the respective animal species, then all their varied compositions of acidic phospholipids must be adequate at promoting the processes of adsorption, film refinement, respreading and collapse characteristic of surfactant. We conclude that this effectively monounsaturated composition of anionic phospholipid molecular species is a common characteristic of mammalian surfactants.

Regulation of Cholinephosphotransferase by Thyroid Hormone

We have demonstrated earlier that thyroid hormone (T3) regulates the activity of cholinephosphotransferase (CPT) in guinea pig lung. This effect of T3 is not organ specific because we found T3 also regulates CPT activity in the guinea pig liver. Northern blot analysis using two oligonucleotide probes, one synthesized on the basis of the yeast CPT gene sequence and another on the basis of partial cDNA clone from guinea pig CPT clone, revealed that T3 stimulates the expression of new CPT mRNA. Studies with transcriptional and translational inhibitors indicated that T3 enhanced the translation of the CPT mRNA as well as translocation of preformed CPT enzyme protein from cytosol to mitochondria. Furthermore, it strengthens our previous finding that yeast CPT and guinea pig CPT have high homology in their sequence as both the oligonucleotide probes gave the similar type of Northern blot in the present study.

Photoprotection of solutions of parenteral nutrition decreases the infused load as well as the urinary excretion of peroxides in premature infants

Light exposure and multivitamins are contributing factors to the generation of peroxides in solutions of parenteral nutrition. This article verifies if peroxides infused with parenteral nutrition are of biological significance in neonates. The mechanisms responsible for the generation of peroxides in total parenteral nutrition solutions are reviewed. The consequences of infused peroxides on an index of oxidant stress and on levels of a central antioxidant are evaluated in an animal model. The effect of photoprotection of parenteral nutrition on a biological marker of redox imbalance is evaluated in the urine of premature infants. Parenteral multivitamins produce a drop in glutathione and an oxidant stress similar to peroxides in the lungs of newborn guinea pigs. Infused peroxides elicited an increased urinary peroxide excretion in infants receiving parenteral nutrition exposed to light. Photoprotection reduced levels of infused and excreted peroxides. The results suggest that peroxides infused with total parenteral nutrition are not fully quenched by premature infants.

Evidence that ranolazine behaves as a weak β 1 - and β 2 -adrenoceptor antagonist in the rat cardiovascular system

The clinical anti-anginal effectiveness of ranolazine is currently being evaluated. However, the mechanism of its anti-ischaemic action is still unclear. The aim of this work was to establish whether ranolazine exerts functional beta-adrenoceptor antagonist activity in the rat cardiovascular system. Radioligand binding studies were performed in rat hearts and guinea-pig lungs for beta1- and beta2-adrenoceptor affinity, respectively. Ranolazine had micromolar affinity for both beta,- and beta2-adrenoceptors (pKi5.8 and 6.3, respectively). Developed tension was measured in isolated rat left atria (electrically driven at 4 Hz) and cumulative concentration/response curves to (+/-)isoprenaline (0.01-1,000 nM) constructed. Ranolazine (0.32-10 microM) surmountably but weakly antagonised isoprenaline-induced positive inotropic responses, with an apparent pA2 of 5.85 (5.69-6.00) and a slope of -0.74 (-0.70 to -0.77). In bivagotomised, atropinised pithed rats, ranolazine per se evoked marked bradycardia at doses above 10 mg/kg i.v. (maximum variation at 80 mg/kg -125+/-15 bpm, n=6, P<0.001) by a mechanism apparently unrelated to blockade of beta1- or beta2-adrenoceptors. Cumulative incremental doses of (+/-)isoprenaline (0.63 ng/kg to 0.16 mg/kg i.v.) administered to pithed rats induced concomitant depressor and chronotropic responses. Animals received either vehicle (saline 0.9% i.v., n=12), atenolol (0.04-2.5 mg/kg i.v., n=6 per dose), ICI 118551 (0.01-0.63 mg/kg i.v., n=6 or 7 per dose), (+/-)propranolol (0.01-0.63 mg/kg i.v., n=6 per dose) or ranolazine (2.5-80 mg/kg i.v., n=6 or 7 per dose) 10 min prior to isoprenaline. Ranolazine dose-dependently and competitively antagonised isoprenaline-induced decreases in diastolic arterial pressure (DAP, dose ratio 12.2 with 80 mg/kg ranolazine) and increases in heart rate (HR, dose ratio 20.3 with 80 mg/kg ranolazine). Collectively, these results demonstrate that ranolazine behaves as a weak beta1- and beta2-adrenoceptor antagonist in the rat cardiovascular system.

Heparin Inhibits Allergen-induced Eosinophil infiltration into Guinea-pig Lung Via a Mechanism Unrelated to its Anticoagulant Activity

There is considerable interest in the discovery of novel molecules for the treatment of allergic diseases and several recent studies have demonstrated that heparin can inhibit airway responses in subjects with asthma. However, heparin is also an anticoagulant which is potentially an unwanted effect in a molecule for treating asthma and allergic diseases. Recently, though, there have been a number of molecules described that are heparin-like but devoid of anticoagulant activity. The aim of this study was to evaluate whether the ability of heparin to inhibit allergen-induced eosinophil infiltration could be mimicked by analogues of heparin, some of which lack anticoagulant activity. We evaluated the effects of heparin and a number of modified heparins for their ability to inhibit allergen induced eosinophil infiltration into airways of suitably sensitised guinea-pigs assessed by bronchoalveolar lavage. Heparin and various modified heparins inhibited allergen-induced eosinophil infiltration into guinea-pig lung, including modified heparin preparations lacking anticoagulant activity. Our results suggest that heparin can inhibit eosinophil infiltration into lung tissue via a mechanism unrelated to its ability to act as an anticoagulant. Our results suggest that it may be possible to develop novel antiinflammatory agents for the treatment of asthma and allergic diseases related to the structure of heparin

Effects of COX-1 and COX-2 inhibitors on eicosanoid biosynthesis and the release of substance P from the guinea-pig isolated perfused lung.

In the guinea-pig isolated perfused lung, co-administration of bradykinin (BK) and histamine causes the release of pro-inflammatory neuropeptides, an effect that is largely dependent on BK-induced formation of prostaglandins. Since it is known that at least two isoenzymes, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) catalyse the conversion of arachidonic acid to prostaglandins (PGs) and thromboxanes, the present study aimed at investigating the effect of selective COX-1 and COX-2 inhibitors on the evoked release of substance P (SP). Lungs were vascularly perfused with oxygenated physiological salt solution containing peptidase inhibitors. BK (0.1 microM) and histamine (100 microM) were added to the perfusate for 10 min and 5 min, respectively. The concentrations of 6-keto-PGF1alpha, cysteinyl-leukotriene (LT), and SP were determined in the outflow by radioimmunoassay. In non-stimulated preparations, indomethacin (2 microM) and the selective COX-1 inhibitor SC-560 (0.03-1 microM) reduced basal release of 6-keto-PGF1alpha, without significantly affecting the release of cysteinyl-LT and SP. The selective COX-2 inhibitors NS-398 (1 microM) or DFU (10 microM) had no significant effect on the basal release of eicosanoids or SP. Co-administration of BK and histamine caused a pronounced increase in the concentration of 6-keto-PGF1alpha and cysteinyl-LT, and SP in the effluate. Under these conditions, indomethacin as well as SC-560 reduced the release of 6-keto-PGF1alpha, enhanced cysteinyl-LT release, and attenuated the release of SP. In contrast, the selective COX-2 inhibitors NS 398 and DFU had no significant effect on the stimulated release of eicosanoids or SP. These results suggest that in the isolated guinea-pig lung, basal prostanoid biosynthesis as well as BK-induced stimulation of prostanoid formation and subsequent facilitation of histamine-induced SP release is primarily mediated by COX-1 without detectable involvement of COX-2.

Denopamine, a beta(1)-adrenergic agonist, increases alveolar fluid clearance in ex vivo rat and guinea pig lungs.

The effect of denopamine, a selective beta(1)-adrenergic agonist, on alveolar fluid clearance was determined in both ex vivo rat and guinea pig lungs. Alveolar fluid clearance was measured by the progressive increase in the concentration of Evans blue-labeled albumin over 1 h at 37 degrees C. Denopamine (10(-6) to 10(-3) M) increased alveolar fluid clearance in a dose-dependent manner in ex vivo rat lungs. Denopamine also stimulated alveolar fluid clearance in guinea pig lungs. Atenolol, a selective beta(1)-adrenergic antagonist, and amiloride, a sodium channel inhibitor, inhibited denopamine-stimulated alveolar fluid clearance. The potency of denopamine was similar to that of similar doses of isoproterenol or terbutaline. Short-term hypoxia (100% nitrogen for 1-2 h) did not alter the stimulatory effect of denopamine. Denopamine (10(-4), 10(-3) M) increased intracellular adenosine 3',5'-cyclic monophosphate levels in cultured rat alveolar type II cells. In summary, denopamine, a selective beta(1)-adrenergic agonist, stimulates alveolar fluid clearance in both ex vivo rat and guinea pig lungs.

Contractile actions of proteinase-activated receptor-derived polypeptides in guinea-pig gastric and lung parenchymal strips: evidence for distinct receptor systems.

1. We have measured the contractile activities and relative potencies (EC(50)s) of six thrombin PAR(1) receptor-derived receptor-activating peptides (PAR-APs): AparafluroFRChaCit-y-NH(2) (Cit-NH(2)); SFLLRNP(P7); SFLLRNP-NH(2) (P7-NH(2)); SFLLR (P5); SFLLR-NH(2) (P5-NH(2)); TFLLR-NH(2) (TF-NH(2)) and a PAR(2) receptor activating peptide [SLIGRL-NH(2) (SL-NH(2))] (a) in a guinea-pig lung peripheral parenchymal strip preparation and (b) in a gastric longitudinal smooth muscle preparation. 2. The relative potencies of the PAR-APs in the lung preparation (Cit-NH(2) congruent with TF-NH(2) congruent with P5-NH(2) > P7 congruent with P5 congruent with P7-NH(2); SL-NH(2) not active) differed appreciably from their relative potencies in the gastric preparation: Cit-NH(2) congruent with TF-NH(2) congruent with P7-NH(2) congruent with P5-NH(2) > P7 congruent with SL-NH(2). 3. The contractile actions of the PAR(1)-selective peptide, TF-NH(2) in the gastric preparation were entirely dependent on extracellular calcium and were blocked by tyrosine kinase inhibitors (genistein, tyrphostin 47/AG213, PP1) and by the cyclooxygenase inhibitor, indomethacin, whereas in the lung preparation, the PAR(1)-mediated contractile response was only partially dependent on extracellular calcium and was refractory to the actions of either tyrosine kinase inhibitors or indomethacin. 4. Partial sequencing of the PAR cDNAs detected by RT - PCR both in whole lung and in the peripheral parenchymal strip bioassay tissue demonstrated the presence of both PAR(1) and PAR(2) mRNA; the expression of PAR(2) was detected by immunohistochemistry. 5. The data point to the presence of distinct receptor systems for the PAR(1)-APs in guinea-pig lung parenchymal and gastric smooth muscle and indicate that PAR(2) does not regulate contractile activity in peripheral parenchymal guinea-pig lung tissue

THE INFLUENCE OF SUSPENSION NEBULIZATION OR INSTILLATION ON PARTICLE UPTAKE BY GUINEA PIG ALVEOLAR MACROPHAGES

Phagocytosis represents a crucial event in the host defense against pathogens. Experimental methods are required that allow a range of particle doses to be delivered. However, it is not clear that these methods result in the same sites of deposition or mechanisms of clearance. The effect of particle administration by nebulization or instillation on the uptake by guinea pig alveolar macrophages (AMs) has been studied. Suspensions of escalating quantities of 1-microm fluorescent polystyrene latex microspheres were delivered by 15 min of nebulization (1.4 x 10(7)-11.1 x 10(7) particles) or instillation (19 x 10(7)-152 x 10(7) particles) into the lungs of guinea pigs. These doses were selected to maximize delivery using each of these methods. Macrophages were collected by alveolar lavage 6 h postadministration. The total number of cells recovered was 3 x 10(6) and the cell viability was >97%, which was measured by trypan blue exclusion. Differential cell counts of lavaged cell suspensions were conducted and results showed no difference for the two methods of administration with various concentrations of latex particles and control samples. The uptake of particles was measured using epifluorescence, confocal microscopy, and flow cytometry. AMs showed a dose-dependent increase in associated particles measured by microscopy and flow cytometry. There was a direct correlation (R(2) =.99) in the phagocytic indices (PIs) measured by flow cytometry and fluorescence microscopy. The PI was 15 times higher after instillation than that obtained after particle nebulization. The percentage of AMs involved in phagocytosis observed after instillation was 55% and after nebulization 23%. The uptake of aerosolized particles by AMs and the number of cells involved in phagocytosis were dependent on the particle dose and the efficiency of aerosol delivery to the lungs.

The Increased Expression of Gelatinolytic Proteases Due to Gigarette Smoking Exposure in the Lung of Guinea Pig

Background Chronic obstructive pulmonary disease(COPD) is one of the major contributors to morbidity and mortality amont the adult population. Cigarette smoking(CS) is undoubtedly the single most important factor in the pathogenesis of COPD. However, its mechanism is unclear. The current hyopthesis regarding the pathogenesis of COPD postulates that an imbalance between proteases and antiproteases leads to the destructive changes in the lung parenchyma. This study had two aims. First, to evaluate the effect of CS exposure on histologic changes of the lung parenchyme, and second, to evaluate the effect of CS exposure on the expression of the gelatinolytic enzymes in BAL fluid cells in guinea pigs. Methods Two groups of five guinea pigs were exposed to the whole smoke of 20 commerical cigarettes per day, 5 hours/day, 5 days/week, for 6 weeks, and 12 weeks, respectively, using a smoking apparatus. Five agematched guinea pigs exposed to room air were used as controls. Five or more sections were microscopically examined(×400) and the number of cellular infiltration of the alveolar wall was measured in order to evaluate the effect of CS exposure on the histologic changes of lung parenchyme. The statistical significance was analyzed by a linear regression method. To evaluate the expression of the gelatinolytic enzymes in intraalveolar cells, BAL fluid was obtained and the intraalveolar cells were separated by centrifugation (500 g for 10 min at 4℃). Two sets of culture plates were loaded with 1×106 intraalveolar cells. One plate, contained 0.1mM EDTA, a inhibitor of matrix metalloproteases(MMPs), and the other plate had no EDTA. Both plates were incubated for 48 hours at 37℃. After incubation, gelatinolytic protease expression in the supernatants was analyzed by gelatin zymography. Results At the end of CS exposure, the level of blood carboxy Hb had increased significantly(4.1g/dl in control group, 24g/dl immediately after CS exposure, 18g/dl 30 min after CS exposure). Alveolar inflammatory cells were identified in the CS exposed guinea pigs. The number of alveolar cellular cells observed in a microscopic field (400×) was 121.4±7.2, 158.0±20.2, 196.8±32.8, in the control, the 6 weeks, and the 12 weeks group, respectively. The increased extent of inflammatory cellular infiltration of the lung parenchema showed a statistically significant linear relationship with the duration of CS exposure(p=0.001, r2=0.675). Several types of gelatinolytic enzymes in the intraalveolar cells of CS exposed guinea pigs were expressed, of which some were inhibited by EDTA. However, the gelatinolytic enzymes were not expressed in the control groups. Conclusion CS exposure increases inflammatory cellular infiltration of the alveolar wall and the expression of gelatinolytic preoteases in guinea pigs. EDTA inhibits some of the gelatinolytic proteases. These findings suggest a possibility that CS exposure may increase MMP expression in the lungs of gunea pigs

Effect of phosphatidylcholine liposome on regeneration of surgical wound in guinea pig lung.

Phosphatidylcholine liposomes in a dose of 25 mg/kg displayed wound-healing properties. They increased the count of alveolar macrophages, lymphocytes, and microvessels in damaged regions and, therefore, attenuated emphysematous changes in the lungs.

Measurements of hyperpolarized gas properties in the lung. Part III: (3)He T(1).

Hyperpolarized (3)He spin-lattice relaxation was investigated in the guinea pig lung using spectroscopy and imaging techniques with a repetitive RF pulse series. T(1) was dominated by interactions with oxygen and was used to measure the alveolar O(2) partial pressure. In animals ventilated with a mixture of 79% (3)He and 21% O(2), T(1) dropped from 19.6 sec in vivo to 14.6 sec after cardiac arrest, reflecting the termination of the intrapulmonary gas exchange. The initial difference in oxygen concentration between inspired and alveolar air, and the temporal decay during apnea were related to functional parameters. Estimates of oxygen uptake were 29 +/- 11 mL min(-1) kg(-1) under normoxic conditions, and 9.0 +/- 2.0 mL min(-1) kg(-1) under hypoxic conditions. Cardiac output was estimated to be 400 +/- 160 mL min(-1) kg(-1). The functional residual capacity derived from spirometric magnetic resonance experiments varied with body mass between 5.4 +/- 0.3 mL and 10.7 +/- 1.1 mL. Magn Reson Med 45:421-430, 2001.

Prevention of reperfusion induced lung injury by L-carnitine

L-Carnitine plays an important role in the transmembrane transport of long chain fatty ascids for it's oxidation and supresses the development of free radical damage. An experimental comparative study isolated guinea pig lungs has been undertaken to determine the probable beneficial effects of adding L-Carnitine to preischemic pulmonary perfusion solutions in lung ischemia-reperfusion. The isolated lungs (n=10 in control group) previously being perfused by oxygenated Krebs Henseleit solution were put in normothermic ischemic conditions. 1 O mmol of L-Carnitine was added into a Krebs-Henseleit solution in the experimental group (n= 10) and after 20 min., perfusion was completed and the lungs were then exposed to normothermic ischemia. After 3 hours of normothermic ischemia, the lungs were perfused with Krebs-Henseleit solution for 20 minutes. Tissue malondialdehyde (MDA), glutathione (GSH) levels and electron microscopic evaluations were held on before the ischemic period and also at the end of reperfusion. MDA and GSH levels of the perfusate were measured before ischemic period and at the end of reperfusion. L-Carnitine administration reduced MDA levels both in tissues and perfusates. in contrast to glutathione levels which is increased. According to our data, the addition of L Carnitine to preischemic pulmonary perfusion solution showed a significant protective effect regarding both ischemic and reperfusion injury.

S-nitrosoglutathione breakdown prevents airway smooth muscle relaxation in the guinea pig.

Airway levels of the endogenous bronchodilator S-nitrosoglutathione (GSNO) are low in children with near-fatal asthma. We hypothesized that GSNO could be broken down in the lung and that this catabolism could inhibit airway smooth muscle relaxation. In our experiments, GSNO was broken down by guinea pig lung homogenates, particularly after ovalbumin sensitization (OS). Two lung protein fractions had catabolic activity. One was NADPH dependent and was more active after OS. The other was NADPH independent and was partially inhibited by aurothioglucose. Guinea pig lung tissue protein fractions with GSNO catabolic activity inhibited GSNO-mediated guinea pig tracheal ring relaxation. The relaxant effect of GSNO was partially restored by aurothioglucose. These observations suggest that catabolism of GSNO in the guinea pig 1) is mediated by lung proteins, 2) is partially upregulated after OS, and 3) may contribute to increased airway smooth muscle tone. We speculate that enzymatic breakdown of GSNO in the lung could contribute to asthma pathophysiology by inhibiting the beneficial effects of GSNO, including its effect on airway smooth muscle tone.

Inhibition of nitric oxide synthesis augments pulmonary oedema in isolated perfused rabbit lung

The role of nitric oxide (NO) in precipitating pulmonary oedema in acute lung injury remains unclear. We have investigated the mechanism of involvement of NO in the maintenance of liquid balance in the isolated rabbit lung. Thirty pairs of lungs were perfused with colloid for up to 6 h, during which pulmonary vascular resistance (PVR) and capillary pressure (PCP) were measured frequently, and time to gain 5 g in weight (t5) was recorded. Four protocols with different perfusate additives were studied: (i) none (control, n = 11); (ii) 10 mmol NG-nitro-L-arginine methyl ester (L-NAME) (n = 6); (iii) 10 mmol L-NAME with 100 mumol lodoxamide, an inhibitor of mast cell degranulation (n = 7); (iv) 10 mmol L-NAME with 10 mumol 8-bromo-3',5'-cyclic guanosine monophosphate (8Br-cGMP), an analogue of cGMP that may reduce vascular permeability by relaxing contractile elements in endothelial cells (n = 6). Neither PVR nor PCP differed between protocols. L-NAME markedly reduced t5 from 248 (27) min (mean (SEM)) in protocol (i) to 144 (5) min in protocol (ii) (P < 0.05). Both lodoxamide (t5 = 178 (7) min) and 8Br-cGMP (t5 = 204 (10) min) substantially corrected the effect of L-NAME (P < 0.005). Results suggest that maintenance of a low permeability by NO may involve mast cell stabilization and endothelial cell relaxation.

Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation

The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H 2O 2 (0, 250, 500 μM) or multivitamins (0, 1%) , as well as parenteral nutrition supplemented with multivitamins (0, 1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.

Nociceptin inhibits capsaicin-induced bronchoconstriction in isolated guinea pig lung

The isolated perfused guinea pig lung was used to investigate the effect of nociceptin against bronchoconstriction elicited by endogenous and exogenous tachykinins. The opioid receptor-like 1 (ORL1) receptor agonist, nociceptin/orphanin FQ (0.001–1 μM) produced a dose-related inhibition of the capsaicin-induced bronchoconstriction (10 −5–10 3 μg) in isolated guinea pig lung ( P<0.05), a response mediated by the release of endogenous tachykinins from lung sensory nerves. The new ORL1 receptor antagonist 1-[(3 R,4 R)-1-Cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2 H-benzimidazol-2-one (J-113397) (0.3 μM) significantly blocked the inhibitory effect of nociceptin/orphanin FQ (0.01 μM) on capsaicin-induced bronchoconstriction, whereas the non-selective opioid receptor antagonist naloxone (1 μM) had no effect. Nociceptin/orphanin FQ (1 μM) did not affect the bronchoconstriction induced exogenously by the tachykinin NK2 receptor agonist neurokinin A. In conclusion, the present data provide evidence that nociceptin inhibits capsaicin-evoked tachykinin release from sensory nerve terminals in guinea pig lung by a prejunctional mechanism. This inhibitory action occurs independently from activation of opioid receptors. The present study also indicates that J-113397 is a potent ORL1 receptor antagonist.

Vitamin C prevents cigarette smoke–induced oxidative damage in vivo

Our recent in vitro results [4] indicate that cigarette smoke induces oxidation of human plasma proteins and extensive oxidative degradation of the guinea pig lung, heart, and liver microsomal proteins, which is almost completely prevented by ascorbic acid. In this paper, we substantiate the in vitro results with in vivo observations. We demonstrate that exposure of subclinical or marginal vitamin C–deficient guinea pigs to cigarette smoke causes oxidation of plasma proteins as well as extensive oxidative degradation of the lung microsomal proteins. Cigarette smoke exposure also results in some discernible damage of the heart microsomal proteins. The oxidative damage has been manifested by SDS-PAGE, accumulation of carbonyl and bityrosine, as well as loss of tryptophan and protein thiols. Cigarette smoke exposure also induces peroxidation of microsomal lipids as evidenced by the formation of conjugated dienes, malondialdehyde, and fluorescent pigment. Cigarette smoke–induced oxidative damage of proteins and peroxidation of lipids are accompanied by marked drop in the tissue ascorbate levels. Protein damage and lipid peroxidation are also observed in cigarette smoke–exposed pair-fed guinea pigs receiving 5 mg vitamin C/animal/day. However, complete protection against protein damage and lipid peroxidation occurs when the guinea pigs are fed 15 mg vitamin C/animal/day. Also, the cigarette smoke–induced oxidative damage of proteins and lipid is reversed after discontinuation of cigarette smoke exposure accompanied by ascorbate therapy. The results, if extrapolated to humans, indicate that comparatively large doses of vitamin C may protect the smokers from cigarette smoke–induced oxidative damage and associated degenerative diseases.

Increased airway responsiveness after skin sensitisation to 3-carene, studied in isolated guinea pig lungs

Inhalation of 3-carene has been shown to induce bronchoconstriction in concentrations not far from the threshold limit value. In this study, one group of guinea-pigs were sensitised by dermal exposure to 3-carene according to the modified Cumulative Contact Enhancement Test protocol and another group of animals was used as controls. Lungs from the skin-sensitised and control guinea-pigs were perfused with diluted autologous blood (13 ml blood/87 ml buffer) and exposed to 3-carene at an air concentration of 3000 mg/m 3. In both groups there was a reduction in compliance and conductance but this reduction was significantly ( P<0.05) more pronounced (2.5–3 times) in lungs obtained from sensitised animals than from control animals. In a previous study with similar design, but with plain buffer instead of diluted autologous blood as perfusate, we found no statistically significant difference in lung bronchoconstriction. Thus, it is concluded that skin sensitisation can increase lung reactivity to 3-carene and that important mediators of this effect seem to be present in the blood.