title: Chymase-dependent conversion of Big endothelin-1 in the mouse in vivo.
abstract: The aim of this study was to identify the role of chymase in the conversion of exogenously administered Big endothelin-1 in the mouse in vivo. Real-time polymerase chain reaction analysis detected mRNA of mucosal mast cell chymases 4 and 5, endothelin-converting enzyme 1a, and neutral endopeptidase 24.11 in pulmonary, cardiac, and aorta homogenates derived from C57BL/6J mice, with the latter tissue expressing the highest levels of both chymase isoforms. Furthermore, hydrolysis of a fluorogenic peptide substrate, Suc-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin, was sensitive to the chymase inhibitors Suc-Val-Pro-Phe(P)(OPh)(2) (200 microM) and chymostatin [(S)-1-carboxy-2-phenylethyl]-carbamoyl-alpha-[2-iminohexahydro-4(S)-pyrimidyl]-(S)-Gly-X-Phe-al, where X can be the amino acid Leu, Val, or Ile) (100 microM) in supernatants extracted from the same tissue homogenates. In anesthetized mice, Big endothelin-1, endothelin-1 (1-31), and endothelin-1 triggered pressor responses (ED(50)s, 0.67, 0.89, and 0.16 nmol/kg) that were all reduced or potentiated by selective endothelin ET(A) or ET(B) receptor antagonists, respectively, BQ-123 (cyclo[D-Asp-Pro-D-Val-Leu-D-Trp]) or BQ-788 (N-[N-[N-[(2,6-dimethyl-1-piperidinyl)carbonyl]-4-methyl-l-leucyl]-1-(methoxycarbonyl)-D-tryptophyl]-d-norleucine sodium salt), each at 1 mg/kg. The pressor responses to big endothelin-1 were significantly reduced by the neutral endopeptidase inhibitor thiorphan (dl-3-mercapto-2-benzylpropanoylglycine) (1 mg/kg) or the endothelin-converting enzyme inhibitor CGS 35066 [alpha-[(S)-(phosphonomethyl)amino]-3-dibenzofuranopropanoic acid] (0.1 mg/kg). In contrast, the responses to endothelin-1 (1-31) were abolished by thiorphan but unaffected by CGS 35066. In addition, Suc-Val-Pro-Phe(P)(OPh)(2) (20-40 mg/kg) reduced, by more than 60%, the hemodynamic response to big endothelin-1 but not to endothelin-1 (1-31) and endothelin-1. Finally, intravenous administration of big endothelin-1 induced Suc-Val-Pro-Phe(P)-(OPh)(2)-sensitive increases in plasma-immunoreactive levels of endothelin-1 (1-31) and endothelin-1. The present study suggests that chymase plays a pivotal role in the conversion and cardiovascular properties of big endothelin-1 in vivo.
authors.affiliation: Département de Pharmacologie, Facultéde médecine et des Sciences de Santé, Universitéde Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Elie
authors.initials: E
authors.lastname: Simard
authors.forename: Denan
authors.initials: D
authors.lastname: Jin
authors.forename: Shinji
authors.initials: S
authors.lastname: Takai
authors.forename: Mizuo
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Isabelle
authors.initials: I
authors.lastname: Brochu
authors.forename: Pedro
authors.initials: P
authors.lastname: D'Orléans-Juste
mesh_terms: D000758:Anesthesia; D000818:Animals; D053818:Chymases / Q000378:metabolism*; D019332:Endothelin-1 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D017466:Receptors, Endothelin / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D012333:RNA, Messenger; D017466:Receptors, Endothelin; D012697:Serine Endopeptidases; C066932:mast cell protease 4; D053818:Chymases