Characteristics and localisation of 125I ion binding in mammalian airways

We have examined some of the binding characteristics and the autoradiographic distribution of binding sites for Na125I (I-Na) in airway tissue from the guinea-pig, monkey, pig, rat, mouse and from man. Basal I-Na (100 pM) binding levels were extremely low. However, in the presence of ascorbic acid (10 microM) or dithiothreitol (10 microM), I-Na binding was markedly increased in guinea-pig trachea, with lesser increases detected in monkey and rat trachea and in monkey and human bronchus. In guinea-pig trachea, ascorbic acid-induced I-Na binding was not saturable within the concentration range 100-620 pM and could not be reduced by washout. Autoradiography revealed that in central airways, I-Na binding was localized at or near the interface of the airway epithelium and submucosa in small clusters, apparently involving one or two cells per focus. The physiological significance of these binding sites is yet to be established, although they may be involved in intracellular iodine storage.     

Contractile properties of synthetic cationic polypeptides in guinea-pig isolated trachea.

1. Purinoceptor agonist-induced currents in untreated (proliferating) and lipopolysaccharide- (LPS; 100 ng ml-1) treated (non-proliferating) rat microglial cells were recorded by the whole-cell patch-clamp technique. 2. In non-proliferating microglia, adenosine (0.01-100 microM), 2-methylthio ATP (3-3000 nM), ATP (0.1-1000 microM), and ATP-gamma-S (1-10 microM), but not alpha,beta-methylene ATP (alpha,beta-MeATP; 100 microM) produced a slow outward current at a holding potential of 0 mV. When K+ was replaced in the pipette solution by an equimolar concentration of Cs+ (150 mM), the 2-methylthio ATP- (300 nM) induced outward current disappeared. The effect of 2-methylthio ATP (300 nM) did not depend on the presence of extracellular Mg2+ (1 mM). The outward current response to 2-methylthio ATP (300 nM) was larger in proliferating than in non-proliferating microglia. 3. ATP (1-1000 microM) evoked a fast inward current at a holding potential of -70 mV in nonproliferating microglia, while adenosine (100-1000 microM) was inactive. When the effects of ATP were compared at 0 and -70 mV, it became evident that ATP is much more potent in evoking the outward current. 4. The 2-methylthio ATP- (300 nM) induced outward current was blocked by suramin (300 microM), but not by 8-(p-sulphophenyl)-theophylline (100 microM), while the adenosine- (1 microM) induced outward current had the reverse sensitivity to these antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of parainfluenza-1 respiratory tract viral infection on endothelin receptor-effector systems in mouse and rat tracheal smooth muscle.

1. In this study we have compared the effects of parainfluenza-1 respiratory tract viral infection on the density and function of ETA and ETB receptors in rat and mouse tracheal airway smooth muscle. 2. The bronchoconstrictor effect of inhaled methacholine was significantly enhanced in virus-infected rats, at both 4 and 12 days post-inoculation. That is, the concentration of methacholine causing an increase in resistance of 100% (PC100 methacholine) was significantly lower in virus-infected animals at both 4 and 12 days post-inoculation (n = 6-8; P < 0.05). 3. Total specific binding of [125I]-endothelin-1 and the relative proportions of ETA and ETB binding sites for [125I]-endothelin-1 were assessed in tracheal airway smooth muscle in parainfluenza-1-infected rats and mice at days 2, 4 and 12 post-inoculation using the ligands BQ-123 (1 microM; ETA receptor-selective) and sarafotoxin S6c (100 nM; ETB receptor-selective). Total specific binding in mice was significantly reduced at day 2 post-inoculation (n = 5; P < 0.05) but not at days 4 and 12 post-inoculation (n = 5). In control mice, the proportions of ETA and ETB binding sites were 53%:47% at day 2 and 43%:57% at day 4 and these were significantly altered by parainfluenza-1 infection such that, the ratios were 81%:19% at day 2 and 89%:11% at day 4 (P < 0.05). By day 12 post-inoculation, the proportion of ETA and ETB binding sites in tracheal smooth muscle from mice infected with parainfluenza-1 was not significantly different from control. In rat tracheal airway smooth muscle, neither total specific binding nor the ETA and ETB binding site ratio (64%:36%) were significantly altered in virus-inoculated rats at days 2, 4 or 12 post-inoculation (n = 5). 4. Parainfluenza-1 infection in mice had no effect on the sensitivity or maximal contractile effect of endothelin-1 in tracheal smooth muscle at days 2, 4 or 12 post-inoculation (n = 4). In contrast, contraction in response to the ETB receptor-selective agonist sarafotoxin S6c was attenuated by 39% at day 2 and by 93% at day 4 post-inoculation (P < 0.05). However, by day 12 post-inoculation, contractions to sarafotoxin S6c were not significantly different between control and virus-infected mice. In parainfluenza-1-infected rats, there were small but significant reductions in the sensitivity to carbachol, endothelin-1 and sarafotoxin S6c whilst the maximal responses to the highest concentrations of these agonists were not significantly altered by virus infection (n = 8). 5. BQ-123 (3 microM) had no significant effect on cumulative concentration-effect curves to endothelin-1 in tracheal preparations from control mice (n = 4) or parainfluenza-1-infected rats (n = 8). In contrast, in tissues taken from virus-infected mice at day 4 post-inoculation, BQ-123 caused a marked 9.6 fold rightward shift in the concentration-effect curve to endothelin-1 (n = 4). 6. In summary, we have demonstrated that parainfluenza-1 infection in mice transiently reduced the density of tracheal airway smooth muscle ETB receptors and this was reflected in reduced responsiveness to the ETB receptor-selective agonist sarafotoxin S6c. In contrast, whilst parainfluenza-1 infection in rats was associated with the pathological features and bronchial hyperresponsiveness common to respiratory tract viral infection, there was no selective down-regulation of ETB receptor expression or functional activity. The reasons for these species differences are not clear, but may relate to differences in the airway inflammatory response to parainfluenza-1 virus.     

Autoradiographic localization of beta-adrenoceptors in pig lung using [125I]-iodocyanopindolol.

The binding of the beta-adrenoceptor radioligand [125I]-iodocyanopindolol (I-CYP) has been studied in pig lung parenchyma and the distribution of binding sites visualised by light microscopic autoradiography. I-CYP binding was saturable (maximum binding capacity Bmax = 51 +/- 3 fmol mg-1 protein), involving sites with high affinity (dissociation constant KD = 73 +/- 10 pM). Specific I-CYP binding was displaceable both by beta-adrenoceptor agonists ((-)-isoprenaline greater than (-)-adrenaline greater than (+/-)-fenoterol greater than (-)-noradrenaline greater than (+)-isoprenaline greater than (+/-)-RO363) and antagonists ((+/-)-propranolol greater than ICI-118551 greater than atenolol), indicating a predominance of beta 2-adrenoceptors. Further analysis showed that displacement data for the beta 1-selective antagonist atenolol and the beta 2-selective antagonist ICI-118551 were fitted best to a 2 binding site model and that both beta 1- and beta 2-adrenoceptors were present in pig lung in the ratio 28:72 respectively. Autoradiographic grains were localized over tissue and were most dense over alveolar walls greater than vascular endothelium greater than vascular smooth muscle greater than bronchial smooth muscle = bronchial epithelium. Atenolol (10(-5) M) caused a 31% reduction in specific grain density over alveolar wall tissue, while a 10 fold lower concentration of ICI-118551 (10(-6) M) caused a 50% decrease. These results are consistent with binding data in pig lung parenchyma demonstrating a mixed population of beta-adrenoceptors with a predominance of the beta 2 subtype.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of macroscopic osteoarthrotic changes and radiographic findings in the acromioclavicular joint

In a total of 108 acromioclavicular articulations from cadavers the osteoarthrotic changes were studied. The articulations were macroscopically and radiographically ranked according to their grade of osteoarthrosis. The two ranking lines were correlated statistically and showed a rank correlation of 0.741. In 38 articulations tomography was also carried out. These articulations were classified into five grades of osteoarthrosis and the macroscopic, conventional radiographic and tomographic gradings were compared. The correlation coefficient for tomography versus macroscopy was 0.714. Tomography versus standard radiography showed a correlation of 0.767 and standard radiography versus macroscopy a correlation of 0.841. The standard radiographic investigation reveals moderate and severe osteoarthrotic changes in the acromioclavicular joint but cannot depict smaller changes. Tomography does not seem to improve the specificity. There is a need for a better radiologic technique in the examination of the acromioclavicular joint. Radiography during some kind of loading might be a practical way of improving the specificity and make it possible to show early osteoarthrosis in the acromioclavicular articulation.     

Epithelium-derived inhibitory factor in human bronchus

The potencies of histamine and methacholine were significantly increased by approximately 2- and 5-fold respectively in human non-diseased isolated bronchi on removal of the epithelium. In contrast, no increases in spasmogen potency were observed following epithelium removal in bronchi obtained from a sample of asthmatic human lung. The failure of epithelium removal to increase asthmatic bronchial sensitivity to histamine may have been due to a reduction in the release of an epithelium-derived inhibitory factor (EpDIF) resulting from disease-induced epithelial damage. A co-axial bioassay system in which endothelium-denuded rat aorta was used as the assay tissue was used to detect the release of a vasorelaxant EpDIF from human bronchial tissue. Histamine (100 microM) and methacholine (25 microM), in the presence of indomethacin (5 microM), reduced phenylephrine-induced tone in endothelium-denuded rat aorta in co-axial assemblies by 75 +/- 11 and 67 +/- 9% respectively. Removal of the bronchial epithelium abolished these responses, indicating that they were mediated by an EpDIF. It is possible that human airway smooth muscle is sensitive to this vasorelaxant EpDIF and that the absence of the source of this factor following epithelium removal caused the increases in sensitivity to spasmogens. Alternatively, the human bronchial epithelium may also release an EpDIF selective for airway smooth muscle.