caa a22 4500 463238702 CHVBK 20180405153306.0 cr unu---uuuuu 170326e20070201xx s 000 0 eng 10.1007/s11259-006-3396-z doi (NATIONALLICENCE)springer-10.1007/s11259-006-3396-z Segment-dependent Expression of Muscarinic Acetylcholine Receptors and G-protein Coupling in the Equine Respiratory Tract [Elektronische Daten] [G. Abraham, C. Kottke, H. Ammer, S. Dhein, F. Ungemach] Muscarinic receptors are considered to be of comparable clinical importance in chronic obstructive pulmonary disease (COPD) in equines and in humans. At present, data are scarce on the expression and distribution of probable subtypes of these receptors and their signalling pathways in airway segments, including lung parenchyma and bronchial and tracheal epithelium with the underlying smooth muscle in horses. Specific [N-methyl-3H]scopolamine chloride ([3H]NMS) binding to all three tissues was saturable and of high affinity, with K D values ranging between 1.6±0.7 and 1.9±0.3 nmol/L. [3H]NMS binding identified a higher density of total muscarinic receptors (fmol/mg protein) in the trachea (720±59 nmol/L) than in bronchi (438±48 nmol/L) or lung (22 ± 3 nmol/L). Competitive binding studies using [3H]NMS and the unlabelled subtype-selective antagonists pirenzepine and telenzepine (M1), methoctramine and himbacine (M2), 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) (M3), tropicamide (M4) and mamba toxin (MT-3) (M4) indicated the presence of at least three muscarinic receptor subtypes in peripheral lung tissue (50:40:24-28%: M2>M3>M1), whereas in bronchus and trachea M2 subtypes (87-90%) predominated over M3 (14-22%), and M1 subtypes were lacking. No differences were found between tissues in high-affinity binding sites for carbachol in the absence (31-36%) or presence of guanosine 5′-triphosphate (GTP) (∼100%). Western blotting for G-protein α-subunits showed a much more robust expression of Gαi1/2 in the trachea (with highest receptor density) than in the lung or bronchi, whereas Gαs-protein was dominantly expressed in bronchus. Concomitantly, carbachol inhibited isoproterenol- and GTP-stimulated adenylyl cyclase activity with increasing muscarinic receptor expression (trachea > bronchi > lung). We conclude that the expression and signalling pathways of muscarinic receptors in the equine respiratory tract are segment-dependent. These receptors might contribute to the pathogenesis of COPD in the horse and could provide potential drug targets for the therapeutic use of anticholinergics in this species. Springer Science + Business Media, Inc., 2007 muscarinic receptors nationallicence G-protein nationallicence adenylyl cyclase nationallicence equine nationallicence lung nationallicence bronchus nationallicence trachea nationallicence radioligand binding nationallicence COB : chronic obstructive bronchitis nationallicence COPD : chronic obstructive pulmonary disease nationallicence 4-DAMP : 4-diphenylacetoxy-N-methylpiperidine nationallicence GPCR : G-protein-coupled receptor nationallicence [3H]NMS : [N-methyl-3H] scopolamine chloride nationallicence RAO : recurrent airway obstruction nationallicence Abraham G. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut Kottke C. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut Ammer H. Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Munich, Germany aut Dhein S. Clinic for Cardiac Surgery, Heart Centre Leipzig, Leipzig University, Leipzig aut Ungemach F. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut Veterinary Research Communications Kluwer Academic Publishers 31/2(2007-02-01), 207-226 0165-7380 31:2<207 2007 31 11259 https://doi.org/10.1007/s11259-006-3396-z text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11259-006-3396-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Abraham G. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut NATIONALLICENCE 700 1- Kottke C. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut NATIONALLICENCE 700 1- Ammer H. Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Munich, Germany aut NATIONALLICENCE 700 1- Dhein S. Clinic for Cardiac Surgery, Heart Centre Leipzig, Leipzig University, Leipzig aut NATIONALLICENCE 700 1- Ungemach F. Institute of Pharmacology, Pharmacy and Toxicology, Leipzig University, Leipzig aut NATIONALLICENCE 773 0- Veterinary Research Communications Kluwer Academic Publishers 31/2(2007-02-01), 207-226 0165-7380 31:2<207 2007 31 11259 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer