title: Phosphoramidon and thiorphan suppress the generation of endothelin (ET) from exogenous big-endothelin by guinea pig Clara cells.
abstract: The formation of endothelins (ET) from exogenous big-ET-1, -2 and -3 was investigated in cultured guinea pig Clara cells. When Clara cells were incubated with 10(-9) or 10(-8) M human big-ET-1 (1-38), the release of ET was 69.9 +/- 7.6 and 221.6 +/- 25 fmol/ml respectively, after 1 h incubation period. Treatment of Clara cells with 1 mM phosphoramidon strongly suppressed (80%) the conversion of big-ET-1 to ET-1 during 1, 2 and 6 h incubation periods. Treatment of Clara cells with thiorphan (1 mM), an inhibitor of neutral endopeptidase, decreased by 44 and 26% the levels of immunoreactive endothelin (ir-ET) in the cell supernatant respectively, after 1 and 2 h incubation periods. When Clara cells were incubated with 10(-8) M human big-ET-2 (1-38), the release of ir-ET was 287.6 +/- 8.9 fmol/ml after a 1 h incubation period. Phosphoramidon and thiorphan (1 mM) reduced the amount of ir-ET generated from exogenous human big-ET-2 (10(-8) M) by 69 and 56%, respectively. When Clara cells were incubated with 10(-8) M human big-ET-3 (1-41), the release of ET was not increased after a 1 h incubation period. Our results suggest that guinea pig Clara cells convert exogenous big-ET-1 and -2 but not big-ET-3 into ET-1 and ET-2, respectively, through metalloproteinases sensitive to both phosphoramidon and thiorphan.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, University of Sherbrooke, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Laporte
authors.forename: P
authors.initials: P
authors.lastname: Sirois
mesh_terms: D000818:Animals; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D019332:Endothelin-1; D016232:Endothelins / Q000378:metabolism*; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006020:Glycopeptides / Q000494:pharmacology*; D006168:Guinea Pigs; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism*; D011863:Radioimmunoassay; D015244:Thiorphan / Q000494:pharmacology*
chemical_list: D019332:Endothelin-1; D016232:Endothelins; D006020:Glycopeptides; D011480:Protease Inhibitors; D011498:Protein Precursors; D015244:Thiorphan; D008666:Metalloendopeptidases; C008890:phosphoramidon