Relationship between endothelin-1 binding site densities and constrictor activities in human and animal airway smooth muscle.
1. Endothelin-1 (ET-1) binding site densities and constrictor activities were compared in airway smooth muscle preparations of human, guinea-pig, rat and mouse. 2. The mean contractile response to 0.3 microM ET-1 (measured as the % maximum response to 10 microM carbachol, % Cmax +/- s.e.mean) and the mean concentration of ET-1 producing 30% Cmax (95% confidence limits) were respectively; 85.9 +/- 5.4% and 3.4 nM (2.4-5.0) for mouse trachea (n = 11), 88.8 +/- 4.7% and 18.2 nM (11.2-25.2) for rat trachea (n = 6), 71.0 +/- 7.1% and 35.2 nM (5.4-231) for human bronchus (n = 3), and 32.3 +/- 3.0% and 241 nM (125-460) for guinea-pig trachea (n = 6). 3. Light microscopic autoradiography revealed specific [125I]-ET-1 binding sites localized to the smooth muscle band, with very low levels of binding associated with cartilage, submucosal and epithelial cells. 4. Quantitative autoradiographic analyses of the concentration-dependence of specific [125I]-ET-1 binding (0.1-2 nM) to smooth muscle revealed similar dissociation constants but markedly different specific binding site densities for the various animal species. The order of densities of specific [125I]-ET-1 binding sites was rat trachea (69.0 +/- 11.2 amol mm-2) greater than human bronchus (42.7 +/- 17.5 amol mm-2) greater than mouse trachea (28.7 +/- 2.6 amol mm-2) greater than guinea-pig trachea (8.3 +/- 1.8 amol mm-2). 5. A positive relationship between [125I]-ET-1 binding site density and ET-1 constrictor activity was observed in airway smooth muscle preparations from rat, human and guinea-pig. The greater sensitivity of mouse trachea to the constrictor actions of ET-1 was not dependent on the release of cyclo-oxygenaseor epithelium-derived constrictor substances, but may have been due to an inter-species difference in the receptor-effector system for ET-1.
Henry
P J
PJ
Department of Pharmacology, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands.
Rigby
P J
PJ
Self
G J
GJ
Preuss
J M
JM
Goldie
R G
RG
D000328:Adult; D000368:Aged; D000818:Animals; D001345:Autoradiography; D001980:Bronchi / Q000187:drug effects; D016232:Endothelins / Q000494:pharmacology; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017466:Receptors, Endothelin; D013045:Species Specificity; D014132:Trachea / Q000187:drug effects
D016232:Endothelins; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin