PubMed Health⌕ Search

Biomedical subjects

D W Hay

Publications and source records attributed to D W Hay.

At least 73 records · Page 4Linked to original sources
PubMed1995

Endothelin-1 receptor density, distribution, and function in human isolated asthmatic airways.

The potent bronchoconstrictor and mitogenic actions of the peptide endothelin-1 (ET-1) on airway smooth muscle may contribute significantly to the bronchial obstruction observed in asthma. However, the status of the receptor-effector systems that mediate these actions of ET-1 in asthmatic airways is currently unknown. Thus, we have used quantitative autoradiographic and isometric-tension recording techniques to evaluate the density, distribution, and function of the specific receptors that mediate the actions of ET-1 in both asthmatic and nonasthmatic airways. Here, we report that similar numbers of specific binding sites for [125I]-ET-1 exist in asthmatic and nonasthmatic airways, with the greatest densities located in airway smooth muscle in both tissue types. The ETB-receptor subtype constituted approximately 82% and 88% of these receptors for ET-1 in asthmatic and nonasthmatic human bronchial smooth muscle, respectively, and mediated contraction in response to this peptide. In addition, a component of ET-1-induced contraction appeared to be mediated by a non-ETB, BQ-123-resistant mechanism. Furthermore, a small population of ETA sites was identified that did not mediate contraction, but which may have a role in ET-1-induced prostanoid release and airway smooth-muscle proliferation. Interestingly, bronchial smooth muscle from asthmatic lung was significantly less sensitive to the contractile effects of ETB receptor activation, consistent with desensitization of this receptor subtype in response to the increased production and release of ET-1 that occurs in this disease.

Adolescent↗
PubMed1995

Effects of intranasal administration of endothelin-1 to allergic and nonallergic individuals.

Endothelin-1 (ET-1), a 21 amino acid peptide, and its receptors are distributed in the mammalian respiratory tract. To examine the responses of human upper airways to ET-1, we investigated the effects of intranasal administration of ET-1 to nine symptomatic allergic and nine nonallergic volunteers. Paper discs were used to administer ET-1 or diluent to one side of the nasal mucosa, and to collect secretions from the ipsilateral (challenged) and contralateral (opposite) nostrils. ET-1 (0.3-10 micrograms), but not diluent, induced dose-dependent bilateral increases in secretion weights, lysozyme secretion, symptoms of rhinorrhea and itch, and sneezing in both populations. ET-1 did not induce albumin secretion, histamine release, or symptoms of nasal congestion. Compared with the nonallergic subjects, allergic individuals sneezed more and had significantly higher bilateral secretion weights, contralateral lysozyme secretion, and symptoms of rhinorrhea following ET-1 provocation. In summary, ET-1 induced symptoms relevant to inflammatory upper airway diseases in allergic and nonallergic subjects. However, responses of allergic subjects were more pronounced, particularly with respect to symptoms associated with neural reflex responses, such as sneezing and contralateral secretion. Therefore, allergic inflammation enhances responsiveness of the nasal mucosa to ET-1.

Administration, Intranasal↗
PubMed1995

Pharmacological characterization of SB 202235, a potent and selective 5-lipoxygenase inhibitor: effects in models of allergic asthma.

The peptidoleukotrienes and leukotriene B4, formed from arachidonic acid through the action of 5-lipoxygenase (5-LO), exert a spectrum of biological effects. It has been proposed that potent and selective 5-LO inhibitors will be effective therapy in diseases in which the peptidoleukotrienes and leukotriene B4 have been implicated, such as asthma and arthritis. The novel compound (S)-N-hydroxy-N-(2,3-dihydro-6-phenylmethoxy-3-benzyofuranyl )urea (SB 202235) was evaluated as a selective inhibitor of 5-LO in a cell-free system as well as in various cellular assays. In addition, the potential therapeutic value of SB 202235 was assessed in preclinical models of allergic asthma. The activity of the 5-LO enzyme isolated from rat basophilic leukemia-1 cells was inhibited by SB 202235 in a concentration-dependent manner with an IC50 value of 1.9 microM. Consistent with its ability to inhibit 5-LO, SB 202235 inhibited the production of leukotriene B4 by human monocytes and in human whole blood (IC50 values of 1.5 microM and 1.1 microM, respectively). The selectivity of SB 202235 was confirmed by its lack of effect against several other enzymes and receptors. SB 202235 potently and effectively inhibited the contraction produced by a single concentration of ovalbumin in guinea pig trachea (IC50 = 20 microM) and of anti-IgE in human bronchus (IC50 = 2 microM). SB 202235 (3-30 microM) also inhibited the contraction of guinea pig trachea in response to increasing concentration of ovalbumin. When administered orally (30 mg/kg) to conscious guinea pigs, SB 202235 attenuated antigen-induced broncho-constriction and the subsequent eosinophil influx.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Phosphodiesterase IV inhibitors as therapy for eosinophil-induced lung injury in asthma.

Asthma is a complex, multifactorial disease that is underpinned by airway inflammation. A variety of cytotoxic substances are released into the airway from infiltrating inflammatory cells, especially the eosinophil. These cytotoxic substances, including reactive oxygen metabolites, produce damage to the airway epithelium, a histologic feature of chronic asthma. Damage to the airway epithelium, in turn, is thought to be a major factor responsible for the development of airway hyperreactivity, a hallmark of asthma. One notable molecular target for novel antiasthmatic drugs is the cyclic AMP-specific phosphodiesterase (PDE) or PDE IV. This isozyme is the predominant form of cyclic nucleotide PDE activity in inflammatory cells. Thus, in view of the putative role of cyclic AMP as an inhibitory second messenger in these cells, PDE IV inhibitors have been shown to suppress inflammatory cell activity. The purpose of the present experiments was to examine the effect of the PDE IV inhibitor, R-rolipram, on three key functions of the guinea pig eosinophil: a) superoxide anion (O2-) production, b) adhesion to human umbilical vein endothelial cells (HUVECs), and c) infiltration into the airway. R-rolipram-elevated eosinophil cyclic AMP content (EC50 = 1.7 microM) and inhibited fMLP-induced O2- production in a concentration-dependent manner (IC50 = 0.3 microM). In contrast, neither siguazodan, a PDE III inhibitor, nor zaprinast, a PDE V inhibitor, had an appreciable effect. R-rolipram (30 microM) also reduced by 25 to 40% the adhesion of eosinophils to HUVECs stimulated with phorbol myristate acetate or tumor necrosis factor-alpha, particularly under conditions in which both cell types were simultaneously exposed to the PDE IV inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

Comparison of phosphodiesterase III, IV and dual III/IV inhibitors on bronchospasm and pulmonary eosinophil influx in guinea pigs.

Selective inhibition of phosphodiesterase (PDE) isozymes has been shown to inhibit inflammatory cell function and relax airway smooth muscle and, thus, may be useful in the therapy of asthma. In guinea pigs sensitized to ovalbumin (OA), the effects of three PDE inhibitors were compared: siguazodan (PDE III selective, IC50 = 0.7 microM), rolipram (PDE IV selective, IC50 = 0.8 microM) and zardaverine (dual PDE III/IV, IC50S = 2.5 microM and 1.1 microM, respectively) against histamine-, leukotriene (LT) D4- and OA-induced bronchospasm in vitro and in vivo. Rolipram or zardaverine (0.1-10 microM), but not siguazodan, inhibited OA-induced contraction of the isolated trachea in a concentration-dependent manner. Rolipram or siguazodan alone (10 microM) were ineffective against histamine- or LTD4-induced contractions. Zardaverine alone (10 microM) or the combination of rolipram and siguazodan (10 microM each) markedly antagonized the contractions elicited by both spasmogens. In anesthesized, ventilated guinea pigs, the i.v. ID50S against OA-induced bronchospasm were: rolipram = 0.2 mg/kg, siguazodan > 10 mg/kg and zardaverine = 2.4 mg/kg. When administered at doses up to 7.5 mg/kg, i.v., rolipram or siguazodan were markedly less effective (i.e., < or = 50% inhibition) than zardaverine (ID50S = 2.4 and 1.7 mg/kg, respectively) at blocking exogenous histamine- or LTD4-induced bronchospasm. However, when administered in combination with siguazodan (5.4 mg/kg, i.v.), rolipram (0.4-5.4 mg/kg) abolished histamine- and LTD4-induced bronchoconstriction. In conscious guinea pigs, zardaverine (5 mg/kg, intragastrically (i.g.) or the combination of rolipram and siguazodan (5 mg/kg each) were substantially more effective than rolipram or siguazodan alone at inhibiting aerosol histamine- or LTD4-induced bronchospasm. In the same animals, rolipram or zardaverine (5 mg/kg, i.g.) but not siguazodan (5 mg/kg, i.g.) markedly inhibited aerosol OA-induced bronchoconstriction. The OA-induced pulmonary eosinophil infiltration in these animals was attenuated by all treatments with zardaverine producing the greatest degree of inhibition. These results indicate that 1) PDE IV inhibitors but not PDE III inhibitors are effective at blocking antigen-induced bronchospasm, 2) compounds that selectively inhibit either PDE III or PDE IV are poor inhibitors of bronchoconstriction elicited by exogenously administered spasmogens, and 3) the combined inhibition of both PDE III and PDE IV isozymes acts in an additive or synergistic manner to inhibit bronchospasm in the guinea pig.

Animals↗
PubMed1994

Differential antagonism of airway contractile responses to prostaglandin (PG)D2 and 9 alpha, 11 beta-PGF2 by atropine, SK&F 88046 and SQ 29,548 in the guinea pig.

PGD2, the predominant prostanoid released from activated human lung mast cells, is metabolized to 9 alpha, 11 beta-PGF2 by an 11-ketoreductase. Both prostanoids contract mammalian airway smooth muscle. In the present study, aerosol administration of PGD2 or 9 alpha, 11 beta-PGF2 (five puffs of 10-50 micrograms/ml) to anesthetized, spontaneously breathing guinea pigs produced significant increases in airway resistance and decreases in dynamic lung compliance. The changes in airway resistance and dynamic lung compliance induced by 50 micrograms/ml were reduced approximately 60% and 25%, respectively, by pretreatment with atropine (1 mg/kg, i.v., -10 min). Pretreatment with the TxA2 receptor antagonist SK&F 88046 (N,N'-bis[7-(3-chlorobenzene aminosulfonyl)-1,2,3,4- tetrahydroisoquinolyl]disulfonylimide) (5 mg/kg, i.v., -10 min), nearly abolished the changes in airway resistance and dynamic lung compliance that were elicited by both agonists. Pretreatment with a TxA2 synthase inhibitor, CGS 13080 (10 mg/kg, i.v., -10 min), had no effect on PGD2- or 9 alpha, 11 beta-PGF2-induced bronchoconstriction, suggesting that these prostanoids did not provoke the release of TxA2. In vitro, PGD2, 9 alpha, 11 beta-PGF2 and a TxA2 mimic, U-44069, produced concentration-dependent contractions of the guinea pig isolated trachea with pD2s of 6.4, 6.0 and 7.2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

Endothelin and the respiratory system.

Pharmacological research involving the endothelin peptides has emphasized their activities in vascular systems, from both physiological and pathophysiological perspectives. However, the endothelins are known also to be synthesized and released from respiratory epithelial cells and to have potent effects in nonvascular components of the respiratory tract. Douglas Hay, Peter Henry and Roy Goldie summarize present understanding of the pharmacology of the endothelins in the respiratory system and assess the potential pathophysiological role in asthma.

Asthma↗
PubMed1993

Endothelin-induced contraction and mediator release in human bronchus.

1. To elucidate the role of acetylcholine and various autacoids in endothelin-1 (ET-1)-induced contraction in human bronchus, the effects of various receptor antagonists were examined. In addition, the ability of ET-1 to stimulate the release of histamine, peptidoleukotrienes and prostanoids was determined. 2. ET-1 was a potent and effective contractile agonist in human bronchus, possessing similar potency and efficacy to leukotriene D4 (LTD4); EC50 (-log M): ET-1 = 7.76 +/- 0.09, n = 7; LTD4 = 8.46 +/- 0.53, n = 7; P > 0.2; maximum response (% 10 microM pre-carbachol): ET-1 = 103.8 +/- 17.4, n = 7; LTD4 = 95.5 +/- 9.3, n = 7; P > 0.6. 3. The cyclo-oxygenase inhibitor, sodium meclofenamate (1 microM) or the potent and selective thromboxane receptor antagonist, SQ 29,548 (1 microM) were without significant effect on ET-1 concentration-response curves. 4. In the presence of sodium meclofenamate (1 microM), the muscarinic receptor antagonist, atropine (1 microM), the platelet activating factor (PAF) receptor antagonist, WEB 2086 (1 microM) or the combination of the H1-histamine receptor antagonist, mepyramine (10 microM) and the leukotriene receptor antagonist, SK&F 104353 (10 microM), were without marked effect on ET-1 concentration-response curves. In addition, the combination of all four receptor antagonists did not antagonize ET-1-induced contraction. 5. ET-1 (0.3 microM) did not stimulate the release of histamine or immunoreactive leukotrienes from human bronchus. 6. ET-1 (0.3 microM) significantly stimulated the release of prostaglandin D2 (PGD2), 9alpha, 11beta PGF2 (PGD2 metabolite), PGE2, 6-keto PGF1alpha (PGI2 metabolite), PGF2alpha, and thromboxane B2 (TxB2) a lower concentration, 10 nM, was without effect on prostanoid release. The production of PGD2 was increased 7.5 fold, whereas the release of the other prostanoids was stimulated only about 1.6 to 2.7 fold.7. These data provide evidence that ET-1 elicits contraction of human isolated bronchus predominantly via a direct mechanism with no significant involvement of the release of acetylcholine, leukotrienes,histamine or PAF. Although ET-1 increased the release of several prostanoids they did not have a significant modulatory effect on the smooth muscle contraction.

Acetylcholine↗
PubMed1993

Relative contributions of direct and indirect mechanisms mediating endothelin-induced contraction of guinea-pig trachea.

1. The present study was undertaken to determine the mechanism of action of endothelin-1 (ET-1)-induced contraction of the guinea-pig isolated trachea. 2. ET-1 (1 nM-0.3 microM) produces a concentration-dependent contraction of guinea-pig trachea with an EC50 of approximately 25 nM. The combination of the peptidoleukotriene receptor antagonist, SK&F 104353 (10 microM) and the H1-histamine receptor antagonist, mepyramine (10 microM), which abolishes antigen-induced contraction in guinea-pig trachea, was without effect on ET-1 concentration-response curves. Furthermore, the platelet-activating factor (PAF) receptor antagonist, WEB 2086, (1 or 10 microM) did not inhibit ET-induced contraction. 3. ET-1 (0.3 microM) did not stimulate histamine or immunoreactive peptidoleukotriene release from guinea-pig isolated trachea. 4. The release of various prostanoids from guinea-pig trachea was increased significantly by ET-1 (0.3 microM); the profile of release was prostaglandin D2 (PGD2) = PGE2 = 6-keto PGF1 alpha (PGI2 metabolite) > thromboxane B2 = PGF2 alpha >> 9 alpha, 11 beta PGF2 (PGD2 metabolite). ET-1-induced release of prostaglandins, which was about 30% of that elicited by antigen in sensitized tissues, was not affected by epithelium removal and was observed in tissues from which the smooth muscle had been removed. Previous studies in our laboratory indicated that indomethacin potentiated contraction produced by high concentrations of ET-1, whereas a thromboxane receptor antagonist was without appreciable effect on ET-1 concentration-response curves. 5. Pretreatment of tissues for 1 h with capsaicin (10 microM), which depletes different sensory neurones, produced a small, but significant, inhibitory effect on ET-1 concentration-response curves in the presence but not the absence of the epithelium. The combination of the NK1 tachykinin receptor antagonist,CP-96,345 (0.1 microM), and the NK2 tachykinin receptor antagonist, SR 48968 (0.1 microM), was without effect on ET-l concentration-response curves but substantially antagonized capsaicin-induced contraction.6. The present data suggest that in guinea-pig isolated trachea, ET- 1 produces contraction predominantly via a direct mechanism: there is no significant contribution of the release of histamine,leukotrienes, PAF, or tachykinins (acting on NK1 or NK2 receptors). Although ET-1 evokes the release of an array of prostanoids from the trachea they do not appear to have a major influence on the contractile response.

Animals↗
PubMed1993

Endothelin receptor subtypes in human and guinea-pig pulmonary tissues.

1. In this study the endothelin (ET) receptor subtypes mediating contractions produced by ET-1 in human and guinea-pig pulmonary tissues were investigated. In addition the receptor responsible for ET-1-induced prostanoid release in human bronchus was determined. 2. In human bronchus and human pulmonary artery ET-1 (0.1 nM-0.3 microM) was a potent and effective contractile agent (pD2 = 7.58 +/- 0.15, n = 6, and 8.48 +/- 0.11, n = 7, respectively). BQ-123 (1-10 microM), a potent and selective ETA receptor antagonist, potently antagonized ET-1-induced contraction in human pulmonary artery (pKB = 6.8 with 1 microM BQ-123, n = 7) but had no effect in human bronchus (n = 6). 3. Sarafotoxin S6c (0.1 nM-0.1 microM), the ETB-selective agonist, did not contract human pulmonary artery (n = 5), but potently and effectively contracted human bronchus: pD2 = 8.41 +/- 0.17, maximum response = 74.4 +/- 3.1% of 10 microM carbachol; n = 5. BQ-123 (1-10 microM) did not antagonize sarafotoxin S6c-induced contraction in human bronchus (n = 5). 4. ET-1 potently contracted guinea-pig trachea, bronchus, pulmonary artery and aorta (pD2 = 8.15 +/- 0.14, 7.72 +/- 0.12, 8.52 +/- 0.12, and 8.18 +/- 0.12, respectively, n = 6-14). BQ-123 (0.1-10 microM)antagonized ET-1-induced contractions in guinea-pig pulmonary artery (pKB = 6.7 with 1 microM BQ-123,n = 6), aorta (pKB = 7.1 with 1 microM BQ-123, n = 6) and trachea (pKB = 6.2 with 1 microM BQ-123, n = 6) butwas without marked effect in bronchus (n = 4). In contrast, sarafotoxin S6c (0.1 nM-0.l microM) did not contract guinea-pig aorta (n = 4) or guinea-pig pulmonary artery (n = 6) but potently and effectively contracted guinea-pig bronchus: pD2= 8.55 +/- 0. 1; maximum contraction = 63.6 +/0 3.1% of 10 microM carbachol,n = 4. Sarafotoxin S6c (0.1 nM-0. 1 microM) was a much less effective agonist in guinea-pig trachea:maximum contraction = 13.9 +/- 2.5% of 10 JM carbachol, n = 4; P< 0.0001, compared to bronchus.Contractions produced by sarafotoxin S6c in guinea-pig bronchus or trachea were unaffected by BQ-123(IO microM, n=4).5. Significant differences were observed in the efficacy, relative to carbachol, but not the potency of sarafotoxin S6c in guinea-pig airways, with a much greater maximum contractile response in bronchus(69.6 +/- 2.4% of 10 microM carbachol, n = 6) or lower region of the trachea (48.5 +/- 5.9% of 10 microM carbachol,n = 6) than in the middle region of the trachea (14.4 +/- 4.0% of 10 microM carbachol, n = 6) or the upper region of the trachea (19.3 +/- 2.7% of 10 microM carbachol, n = 6). There were minimal regional differences in either ET-1-induced contraction or the potency of BQ-123 (3 microM) for inhibition of responses to ET-1 in guinea-pig airways.6. Release of various prostanoids in human bronchus induced by ET-1 (0.3 microM) was essentially abolished with 10 IM BQ-123.7. These data provide evidence that distinct ET receptors mediate ET-1-induced contraction in human pulmonary artery, guinea-pig pulmonary artery and guinea-pig aorta (ETA subtype) compared with human bronchus and guinea-pig bronchus (non-ETA, perhaps ETB subtype). Contractions to ET-1 in guinea-pig trachea appear to involve both ETA and non-ETA (ETB?) receptor subtypes. Furthermore,regional differences appear to exist in the relative distribution of ET receptor subtypes in guinea-pig airways. In human bronchus ET-1-induced prostanoid release, unlike the contractile response, appears to be mediated via ETA receptor activation.

Animals↗
PubMed1993

Identification, characterization and functional role of phosphodiesterase isozymes in human airway smooth muscle.

In the present study phosphodiesterase (PDE) isozymes in human airway smooth muscle were isolated, identified and characterized, and the functional roles of these isozymes in intact bronchi were evaluated by using isozyme-selective PDE inhibitors. PDE isozymes in human trachealis were isolated by using a combination of DEAE-Sepharose and calmodulin-Sepharose affinity chromatography, and were identified based upon their kinetic characteristics as well as their sensitivity to allosteric modulators and isozyme-selective PDE inhibitors. By using this approach, six distinct isozymes were identified: two calmodulin-stimulated PDEs (PDE I alpha and PDE I beta), cyclic GMP (cGMP)-stimulated PDE (PDE II), cGMP-inhibited PDE (PDE III), cyclic AMP (cAMP)-specific PDE (PDE IV) and cGMP-specific PDE (PDE V). PDEs III and IV were the major cAMP-hydrolyzing enzymes present, whereas PDEs I alpha, I beta and V accounted for most of the cGMP-hydrolytic activity. In carbachol-precontracted small (< 0.5-2 mm diameter) or large (4-15 mm diameter) human bronchus, zaprinast (10 nM-30 microM), the selective PDE V inhibitor, was without marked relaxant activity (< 13%), whereas rolipram (30 microM), the selective PDE IV inhibitor, produced approximately 25% relaxation in both preparations. Siguazodan was a significantly more effective relaxant than zaprinast or rolipram in large bronchus, producing a maximum relaxation of 77 +/- 15% at a concentration of 30 microM, whereas in small bronchus 30 microM siguazodan elicited 20 +/- 6% relaxation. Similar results were obtained in large bronchi contracted with leukotriene (LT) D4 (0.1 microM). The ability of isozyme-selective PDE inhibitors to potentiate agonist-induced relaxation was studied in LTD4-contracted large bronchi. Siguazodan (10 microM), but not rolipram (10 microM) or zaprinast (10 microM), potentiated the relaxant response in LTD4-contracted large bronchus to isoproterenol, a beta adrenoceptor agonist thought to induce relaxation via a cAMP-mediated mechanism. In contrast, zaprinast (10 microM), but not siguazodan (10 microM), potentiated relaxation induced by sodium nitroprusside, a nitrovasodilator that relaxes airway smooth muscle via a cGMP-mediated mechanism. The most striking observation from functional studies was that the combination of rolipram and siguazodan produced a much greater relaxation of small or large human bronchi than either agent alone, indicating an interaction between PDE III and PDE IV inhibitors that was at least additive and, in some cases, synergistic.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromatography, Affinity↗
PubMed1993

Molecular species of lecithins in human gallbladder bile.

Using a precise high performance liquid chromatography (HPLC) technique, we identified the molecular species of lecithins in gallbladder biles from patients with cholesterol gallstones (n = 29), pigment gallstones (n = 9), morbid obesity (n = 5), and "controls" (n = 10). The major lecithin species identified in all groups, in descending rank order as represented by the fatty acids in the sn-1 and sn-2 positions, were 16:0-18:2, 16:0-18:1, 16:0-20:4, 18:0-18:2, and 18:1-18:2. Lecithin species were found to be more numerous and in substantially different proportions than reported by previous investigators. No significant differences were found between any biliary lecithin species in the cholesterol and pigment stone groups. However, compared with controls, both cholesterol and pigment stone patients had smaller proportions of 16:0-20:4, the principal arachidonyl lecithin species. Using the HPLC elution sequence for quantifying the hydrophilic-hydrophobic balance, we developed a Hydrophobic Index for lecithin species in each bile based upon the principles proposed by D. M. Heuman for bile salt species. Hydrophobic indices of bile salts and lecithin were positively correlated (r = 0.48, R2 = 0.23, P = 0.0002) suggesting that more hydrophobic bile salts were associated with biliary secretion of more hydrophobic lecithins. The most hydrophobic major lecithin species, 18:0-18:2, was present in greater proportions in biles with cholesterol monohydrate crystals in their sediments and in those with cholesterol saturation indices greater than one. This work provides rigorous separation, identification, and quantitation of the lecithin species in human gallbladder bile from a large cohort of patients but, apart from a more hydrophobic bile salt pattern coupling more hydrophobic lecithins, we fail to identify any relationships of biomedical importance between lecithin species and other major biliary constituents.

Bile↗
PubMed1992

Effects of methoxamine and barium on 45Ca2+ fluxes in the rat vas deferens.

The aim of this study was to determine whether methoxamine and barium stimulate 45Ca2+ uptake or efflux in the rat vas deferens in a manner that correlates with their contractile activity, and whether 45Ca2+ movements are inhibited by verapamil or nifedipine. Basal La(3+)-resistant (cellular) 45Ca2+ uptake was significantly greater in the epididymal half (791 +/- 27 nmol g-1) than in the prostatic half (654 +/- 14 nmol g-1) of the rat vas deferens and was unaffected by verapamil (61 microM) or nifedipine (14 microM). Methoxamine (8 microM) was without effect on 45Ca2+ uptake in either half but BaCl2 (1 mM) increased 45Ca2+ uptake by 31% in the prostatic half and by 22% in the epididymal half. The barium-induced increases in 45Ca2+ uptake were markedly reduced or abolished by verapamil (2 microM) or nifedipine (0.3 microM), which at these concentrations have no effect on the rhythmic contractions but abolish the initial small phasic contraction induced by barium. The basal rate of 45Ca2+ efflux from the intact vas deferens (into Ca2+ containing Krebs-Henseleit solution or into Ca-free Krebs-Henseleit solution +/- EGTA 0.05 mM) was not affected by verapamil (61 microM) or nifedipine (14 microM). Methoxamine (8 microM) produced a marked, transient and reversible increase in 45Ca2+ efflux into 2.5 mM CaCl2 Krebs-Henseleit in 50% of the intact vasa deferentia examined which was augmented by verapamil (61 microM). BaCl2 (1 mM) produced a small increase in 45Ca2+ efflux into Ca(2+)-containing and Ca(2+)-free Krebs-Henseleit solutions from some intact vasa deferentia and this was not inhibited by nifedipine (14 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

SK&F 104353, a selective leukotriene receptor antagonist, inhibits leukotriene D4- and antigen-induced bronchoconstriction in cynomolgus monkeys.

The ability of SK&F 104353 to prevent and reverse leukotriene (LT) D4- and antigen (Ag)-induced bronchoconstriction was examined in anesthetized, spontaneously breathing cynomolgus monkeys. Aerosol administration of LTD4 (10 micrograms/ml; 20 breaths) produced a sustained increase in pulmonary resistance and decrease in dynamic lung compliance. Aerosolized SK&F 104353 (150 breaths, 0.3 or 4.4 mg/ml) administered 15 min prior to LTD4 challenge antagonized these changes in a dose-dependent manner. When given intravenously 6 min after LTD4, SK&F 104353 (5 mg/kg) rapidly and completely reversed the ongoing bronchoconstriction. In mepyramine-pretreated (2 mg/kg i.v.) monkeys sensitive to aerosolized Ascaris suum Ag, intravenously administered SK&F 104353 (5 mg/kg) substantially reversed, but did not abolish, Ag-induced bronchoconstriction when administered 12 min after the Ag challenge. In contrast, SK&F 104353 (5 mg/kg i.v.) did not reverse Ag-induced bronchoconstriction in animals that had not been pretreated with mepyramine. Similar results were obtained when SK&F 104353 (20 mg/kg i.v.) was administered (as a pretreatment) 5 min prior to Ag under these conditions. Thus, SK&F 104353 reduced Ag-induced bronchoconstriction in mepyramine-pretreated monkeys, but had little effect in the absence of mepyramine. The data suggest that LTs, in addition to histamine, play a role in allergic bronchoconstriction in cynomolgus monkeys.

Administration, Inhalation↗
PubMed1992

Evidence that epithelium-dependent relaxation of vascular smooth muscle detected by co-axial bioassays is not attributable to hypoxia.

1. The present study was undertaken to examine further the contribution of hypoxia to airway epithelium-dependent relaxation of rat aorta in the co-axial bioassay. 2. Endothelium-denuded rat aorta contracted with phenylephrine (0.05 microM) relaxed in a time-dependent manner (t1/2 = 8.3 +/- 0.4 min, n = 38) when the bathing solution was bubbled with 95% N2 and 5% CO2. In co-axial bioassays, the t1/2 for histamine (100 microM; guinea-pig trachea)- and methacholine (100 microM; rabbit bronchus)- induced relaxation was 1.9 +/- 0.2 min (n = 14) and 1.2 +/- 0.1 min (n = 26), respectively. 3. Hypoxia-induced relaxation was not associated with a rise in intracellular guanosine 3':5'-cyclic monophosphate (cyclic GMP). This contrasts with previous findings of an elevation in cyclic GMP associated with epithelium-dependent relaxation of rat aorta in co-axial bioassays. 4. Hypoxia-induced vascular relaxation was antagonized by the ATP-sensitive K+ channel blocker, glibenclamide (100 microM). In contrast, glibenclamide (100 microM) failed to inhibit histamine (100 microM; guinea-pig trachea)- and methacholine (0.1-100 microM; rabbit bronchus)-induced release of epithelium-derived inhibitory factor (EpDIF), in co-axial bioassays. Glibenclamide (100 microM) antagonized BRL 38227 (lemakalin), but not isoprenaline-induced relaxation of phenylephrine-contracted rat aorta. 5. These data strongly suggest that the airway epithelium-dependent relaxant responses observed in co-axial bioassays cannot be attributed to hypoxia.

Animals↗
PubMed1992

Correlation between airway epithelium-induced relaxation of rat aorta in the co-axial bioassay and cyclic nucleotide levels.

1. In co-axial bioassays, in the presence of indomethacin, addition of histamine (100 microM) or methacholine (100 microM) to guinea-pig trachea produced an epithelium-dependent relaxation of precontracted rat aorta which was associated with an approximately 2 fold elevation in tissue levels of guanosine 3':5'-cyclic monophosphate (cyclic GMP). Removal of the airway epithelium abolished the histamine-induced relaxation of rat aorta and the associated increase in intracellular cyclic GMP. 2. Epithelium-dependent relaxation was not associated with altered adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels in rat aorta. Unstimulated intact or denuded guinea-pig trachea also did not affect the levels of cyclic AMP or cyclic GMP in rat aorta. 3. Methylene blue (10 microM) abolished the methacholine-induced, endothelium-derived relaxing factor (EDRF)-mediated rise in intracellular cyclic GMP in rat endothelium-intact aorta alone. In contrast, methylene blue (10 microM) did not affect the methacholine-induced epithelium-dependent rise in intracellular cyclic GMP in rat endothelium-denuded aorta in the co-axial bioassay. 4. Relaxation of the rat aorta without endothelium was associated with increased levels of cyclic GMP (but not cyclic AMP) in response to sodium nitroprusside (5 nM) and of cyclic AMP (but not cyclic GMP) in response to isoprenaline (1 microM). 5. These results provide evidence that the postulated epithelium-derived inhibitory factor (EpDIF) may produce relaxation of vascular tissue via elevation in cyclic GMP levels. Furthermore, some data suggest that EpDIF may act by stimulation of the particulate, rather than the soluble form of guanylate cyclase.

Animals↗
PubMed1992

Pharmacological evidence for distinct endothelin receptors in guinea-pig bronchus and aorta.

The ETA receptor antagonist, BQ-123 (1 microM) potently antagonized endothelin-1 (ET-1) concentration-response curves in guinea-pig aorta (pKB = 7.1). However, 10 microM BQ-123 was without effect on ET-1-induced contractions in guinea-pig bronchus. The ETB-selective agonist, sarafotoxin S6c did not contract the aorta but was a potent and effective contractile agonist in the bronchus. BQ-123 (10 microM) was without effect on sarafotoxin S6c-induced contractions in the bronchus. These data provide evidence for distinct endothelin receptors in guinea-pig aorta and bronchus, which appear to be predominantly of the ETA and non-ETA, perhaps ETB, subtypes, respectively.

Animals↗