RECEPTORS FOR ENDOTHELIN-1 IN ASTHMATIC HUMAN PERIPHERAL LUNG

[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.