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

In control lung homogenates, optimal specific binding of [(125)]endothelin- 1 and minimal filter binding was achieved using 50 mu g/ml bacitracin, 30 m u M phenylmethylsulphonyl fluoride (PMSF) and 10 mM EDTA. In post-mortem ti ssue (8, 16, and 32 h), no significant changes were seen in ETA receptor af finity (K-d) or number (B-max) control and 32 h K-d = 309 +/- 75, 225 +/- 3 2 pM and B-max = 173 +/- 42, 185 +/- 17 fmol/mg protein, respectively. Auto radiographic binding sites for [(125)]endothelin-1 were densely expressed o n bronchiolar smooth muscle and parenchyma with moderate binding on epithel ium and blood vessels. Histologic sections of post-mortem lung showed minim al deterioration of structures expressing ETA binding sites. Hence the ETA receptor is stable in the rat lung for up to 32 h post-mortem. (C) 2000 Els evier Science Inc. All rights reserved.