Distribution of substance P binding sites in equine airways.
Autoradiography with [125I]-Bolton Hunter substance P ([I]-BHSP) was used to detect substance P binding sites in the equine lung. Specific [I]-BHSP binding sites were very dense over small bronchial vessels, tracheobronchial glands and airway epithelium in large and small airways. The density of [I]-BHSP binding sites over airway smooth muscle was much lower than in the preceding tissues. Competition with an excess of either a specific neurokinin 1 receptor agonist, or a specific neurokinin 2 receptor agonist indicated that most specific [I]-BHSP binding sites in the equine lung represent neurokinin 1 receptors. The receptor-mediated effects of substance P in the equine lung are most likely to involve regulation of vascular tone and airway secretions based upon the density of specific [I]-BHSP binding sites in these tissues. Activation of intrapulmonary afferent nerves containing Substance P by noxious stimuli such as inhaled allergens or irritants may lead to increased mucus secretion and decreased airway diameter due to vascular congestion.
Department of Anatomy, College of Veterinary Medicine, Michigan State University, East Lansing 48823, USA.
I M
IM
Sonea
R M
RM
Bowker
N E
NE
Robinson
D000818:Animals; D001345:Autoradiography / Q000662:veterinary; D001665:Binding Sites; D001980:Bronchi / Q000378:metabolism*; D003720:Densitometry / Q000662:veterinary; D005260:Female; D006736:Horses / Q000378:metabolism*; D008297:Male; D013373:Substance P / Q000378:metabolism*
D013373:Substance P