Binding characteristics of endothelin ET A receptors in normal and post-mortem rat lung

Abstract

In control lung homogenates, optimal specific binding of [ 125I]endothelin-1 and minimal filter binding was achieved using 50 μg/ml bacitracin, 30 μM phenylmethylsulphonyl fluoride (PMSF) and 10 mM EDTA. In post-mortem tissue (8, 16, and 32 h), no significant changes were seen in ET A receptor affinity ( K d) or number ( B max): control and 32 h K d = 309 ± 75, 225 ± 32 pM and B max = 173 ± 42, 185 ± 17 fmol/mg protein, respectively. Autoradiographic binding sites for [ 125I]endothelin-1 were densely expressed on bronchiolar smooth muscle and parenchyma with moderate binding on epithelium and blood vessels. Histologic sections of post-mortem lung showed minimal deterioration of structures expressing ET A binding sites. Hence the ET A receptor is stable in the rat lung for up to 32 h post-mortem.