Chloride secretory response of cystic fibrosis human airway epithelia. Preservation of calcium but not protein kinase C- and A-dependent mechanisms.
Because the defect in Cl- secretion exhibited by cystic fibrosis (CF) epithelia reflects regulatory rather than conductive abnormalities of an apical membrane Cl- channel, we investigated the role of different regulatory pathways in the activation of Cl- secretion in freshly excised normal and CF nasal epithelia mounted in Ussing chambers. A beta agonist (isoproterenol [ISO]), a Ca2+ ionophore (A23187), and a phorbol ester (PMA) were all effective Cl- secretagogues in normal human nasal epithelia. Agonist addition studies indicated that ISO and PMA but not A23187 may share a common regulatory pathway. In contrast, only A23187 induced Cl- secretion in CF epithelia. Bradykinin raised cytosolic Ca2+ and induced Cl- secretion in both normal and CF tissues, indicating that receptor gated Ca2+ dependent Cl- secretory mechanisms were preserved in CF. The defective Cl- secretory response in CF epithelia to ISO and PMA did not reflect abnormalities in cAMP-dependent (A) and phospholipid Ca2+-dependent (C) kinase activities. We conclude that (a) a Ca2+-sensitive mechanism for regulating Cl- secretion is maintained in CF airway epithelia, and (b) a regulatory pathway shared by two distinct protein kinases is defective in CF, indicating that the CF genetic lesion is not tightly coupled to a single (e.g., cAMP dependent) regulatory mechanism.
Boucher
R C
RC
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27599.
Cheng
E H
EH
Paradiso
A M
AM
Stutts
M J
MJ
Knowles
M R
MR
Earp
H S
HS
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000293:Adolescent; D000328:Adult; D000584:Amiloride / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002648:Child; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis; D003550:Cystic Fibrosis / Q000503:physiopathology*; D004553:Electric Conductivity; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009297:Nasal Mucosa / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002712:Chlorides; D000001:Calcimycin; D000584:Amiloride; D000242:Cyclic AMP; D011493:Protein Kinase C; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine