title: Differing effects of cGMP and cAMP on ion transport across flounder intestine.
abstract: The intestinal epithelium of the winter flounder is highly cation selective and actively absorbs NaCl via a bumetanide-sensitive (Na + K + 2Cl) cotransport system; it also actively secretes K+. Combined addition of adenosine 3',5'-cyclic monophosphate (cAMP) and theophylline was previously shown to partially inhibit NaCl absorption and to increase passive Cl- permeability. Because theophylline increases cyclic GMP (cGMP) and cAMP concentrations, we compared the effects of the 8-Bromo analogues of these two nucleotides on ion transport. cGMP inhibits Cl- absorption, K+ secretion, and Cl- and K+ influx across the brush border as effectively as do furosemide and bumetanide. Even at maximal doses, cAMP is less effective than cGMP in inhibiting ion transport; however, unlike cGMP, it abolishes the cation selectivity of the epithelium by greatly increasing Cl- permeability. The effects of the two nucleotides are not additive with each other or with those of bumetanide, although cGMP or bumetanide can further inhibit transport in cAMP-treated tissues.
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D005399:Fishes; D007408:Intestinal Absorption / Q000187:drug effects*; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology
chemical_list: D002712:Chlorides; D002034:Bumetanide; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D012964:Sodium; D013806:Theophylline; D000242:Cyclic AMP; D006152:Cyclic GMP; D012413:Rubidium; D011188:Potassium