title: Synthesis and vectorial export of cGMP in airway epithelium: expression of soluble and CNP-specific guanylate cyclases.
abstract: Guanosine 5'-cyclic monophosphate (cGMP) is an important modulator of fluid balance in many epithelia. We examined its metabolism in primary cultures of human airway epithelia. Sodium nitroprusside increased cGMP levels 30-fold, suggesting that the respiratory epithelium expresses a soluble guanylate cyclase; however, endogenous nitric oxide production was not detected. cGMP levels could also be increased by C-type natriuretic peptide (CNP), but not by atrial natriuretic peptide, brain natriuretic peptide, or Escherichia coli heat-stable enterotoxin, indicating expression of a CNP-specific membrane-bound guanylate cyclase. The one-half effective concentration for CNP was 40 nM and the maximal velocity was 56.7 pmol cGMP.mg protein-1.h-1. After CNP stimulation, approximately 60% of the total synthesized cGMP was preferentially exported from the polarized epithelial cells across the basolateral membrane by a probenecid-sensitive process. Isoproterenol-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) export revealed a similar export pattern and probenecid sensitivity, although a lower efficiency of export (27% of total cAMP was exported). Consistent with previous reports, export of neither cyclic nucleotide was saturable at the concentrations tested. We conclude that the respiratory epithelium expresses a soluble guanylate cyclase, a CNP-specific receptor, and a novel vectorial cyclic nucleotide export mechanism.
authors.affiliation: Departments of Medicine and Physiology, University of North Carolina at Chapel Hill 27599.
authors.forename: C A
authors.initials: CA
authors.lastname: Geary
authors.forename: M F
authors.initials: MF
authors.lastname: Goy
authors.forename: R C
authors.initials: RC
authors.lastname: Boucher
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006162:Guanylate Cyclase / Q000096:biosynthesis*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020098:Natriuretic Peptide, C-Type; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; D000242:Cyclic AMP; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine