[I-125]-endothelin-1 ([I-125]-ET-1) binding was assessed by autoradiog
raphy in peripheral airway smooth muscle and alveolar wall tissue in h
uman non-asthmatic and asthmatic peripheral lung. Levels of specific b
inding to these structures were similar in both non-asthmatic and asth
matic lung. The use of the receptor subtype-selective ligands, BQ-123
(ET(A)) and sarafotoxin S6c (ET(B)), demonstrated the existence of bot
h ET(A) and ET(B) sites in airway smooth muscle and in alveoli. In air
way smooth muscle from both sources, the great majority of sites were
of the ET(B) subtype. Quantitative analyses of asthmatic and non-asthm
atic alveolar wall tissue demonstrated that 29-32% of specific [I-125]
-ET-1 binding was to ET(A) sites and 68-71% was to ET(B) sites. Thus,
asthma was not associated with any significant alteration in the densi
ties of ET(A) and ET(B) receptors in peripheral human lung.