title: The effect of theophylline on intestinal bicarbonate transport measured by pH stat in Amphiuma.
abstract: 1. The influence of theophylline on the mucosa to serosa and serosa to mucosa fluxes of HCO3- were measured by the pH stat technique in isolated segments of proximal small intestine from Amphiuma maintained under short-circuited conditions. The mucosal or serosal fluid was exposed to media containing 25 mM-HCO3- (pH 7.4) while the pH of unbuffered media in the opposite compartment was maintained by addition of acid. 2. Theophylline significantly increased the secretory flux of HCO3- and significantly reduced the absorptive flux when measured in Cl- -free (SO4(2-)) media. 3. In normal media theophylline did not alter the secretory flux but significantly lowered the absorptive flux of HCO3-. 4. Acetazolamide (0.1 mM) inhibited the theophylline-stimulated secretory flux of HCO3- and reduced the effect of theophylline on the absorptive flux. 5. In normal intestine there was an inequality between the secretory or absorptive HCO3- flux and the short-circuit current (Isc) consistent with the presence of Cl- absorption. After addition of theophylline the Isc was more nearly equal to the net secretory or absorptive HCO3- flux. 6. Exogenous cyclic AMP had effects identical with theophylline. 7. The results provide strong evidence that elevation of cyclic AMP stimulates net HCO3- secretion in urodele small intestine and provide indirect evidence that Cl- absorption is simultaneously reduced.
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology*; D014562:Caudata / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D013806:Theophylline; D000242:Cyclic AMP; D000086:Acetazolamide