RECEPTORS FOR ENDOTHELIN-1 IN ASTHMATIC HUMAN PERIPHERAL LUNG

[I-125]-endothelin-1 ([I-125]-ET-1) binding was assessed by autoradiography in peripheral airway smooth muscle and alveolar wall tissue in human non-asthmatic and asthmatic peripheral lung. Levels of specific binding to these structures were similar in both non-asthmatic and asthmatic lung. The use of the receptor subtype-selective ligands, BQ-123 (ET(A)) and sarafotoxin S6c (ET(B)), demonstrated the existence of both ET(A) and ET(B) sites in airway smooth muscle and in alveoli. In airway smooth muscle from both sources, the great majority of sites were of the ET(B) subtype. Quantitative analyses of asthmatic and non-asthmatic 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 densities of ET(A) and ET(B) receptors in peripheral human lung.