Am. J. Respir. Cell Mol. Biol., Vol 14, No. 4, Apr 1996, 356-362.
Guinea pig Clara cells secrete endothelin 1 through a phosphoramidon- sensitive pathway
J Laporte, P D'Orleans-Juste and P Sirois
Department of Pharmacology, Medical School, University of Sherbrooke, Sherbrooke, Quebec, Canada.
We have developed a method to harvest and culture Clara cells isolated from
guinea pig lungs. Their identity was confirmed by the presence of CC16kD
protein specific for these cells; we studied their capacity to generate
endothelin 1 (ET-1). Using monoclonal antibody and immunofluorescence
techniques, ET-1 was localized in these cultured Clara cells. The basal
release of immunoreactive endothelin (ir-ET), measured by radioimmunoassay,
from cultured Clara cells incubated for 2, 6, and 10 h was 74.8 +/- 11.1,
230.0 +/- 32.0 and 331.0 +/- 22.9 pg/ml, respectively. Treatment of Clara
cells with phosphoramidon (100 microM), an inhibitor of the
endothelin-converting enzyme, caused a significant reduction of the ir-ET
release by 40% after a 6-h incubation period (P<0.01). Following
treatment with 1 mM phosphoramidon, ir-ET was decreased by 73% and 76%
after 6- and 10-h incubation periods, respectively (P<0.01). In
contrast, treatment with thiorphan (1 mM), an inhibitor of neutral
endopeptidase, increased the levels of ir-ET in the cell supernatant.
High-performance liquid chromatography of supernatants from cultured Clara
cells revealed one peak corresponding to the retention time of synthetic
ET-1. This peak was greatly reduced following treatment of the cells with
phosphoramidon (1 mM) but not with thiorphan (1 mM). Our results suggest
that Clara cells release ET-1, a potent bronchoconstrictive agent.
Furthermore, the synthesis of ET-1 is dependent on a
phosphoramidon-sensitive endothelin-converting enzyme. Secretion of this
peptide by Clara cells may play a role, directly or indirectly, in lung
pathophysiology.
