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  • Title: Effects of cyclic AMP, ouabain and furosemide on ion transport in isolated canine gastric mucosa.
    Author: Kuo YJ, Shanbour LL.
    Journal: J Physiol; 1980 Dec; 309():29-43. PubMed ID: 6265625.
    Abstract:
    1. Cyclic AMP (10 mM), present in the serosal solution of isolated dog gastric mucosa, increased potential difference (p.d.), short-circuit current (ISC), net flux of Na+ from the mucosal to serosal side, and the unidirectional flux of K+ from the mucosal to serosal side. Cyclic AMP did not stimulate H+ or Cl- secretion. 2. Dibutyryl cyclic AMP (DBcAMP, 1 mM) or theophylline (2 mM), present in the serosal solution, stimulated H+ and Cl- secretion, decreased p.d., ISC and electrical resistance. These compounds had no effect on Na+ transport. The stimulatory effect of DBcAMP on H+ secretion was still present after pretreatment with cimetidine or atropine. 3. Ouabain abolished both the p.d. and ISC of the histamine-stimulated gastric mucosa. The mucosal to serosal flux of Na+ and the serosal to mucosal flux of Cl- were significantly decreased in the presence of ouabain. Ouabain caused an increase in the serosal to mucosal flux of K+ and high concentrations caused a significant reduction in H+ secretion. 4. Furosemide (10(-4) M) decreased p.d., ISC and net flux of Na+. Higher concentrations inhibited the net flux of Cl- from the serosal to mucosal side. 5. These results suggest that in isolated dog gastric mucosa, (1) both DBcAMP and theophylline may increase intracellular cyclic AMP to stimulate H+ and Cl- secretion, (2) cyclic AMP, outside the serosal membrane, stimulates active transport of Na+; in contrast, ouabain inhibits this active process predominantly, (3) the selective action of furosemide on Na+ transport indicates that Na+ and Cl- move via separate transport pathways across the serosal border.
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