The effect of theophylline on intestinal bicarbonate transport measured by pH stat in Amphiuma.

Abstract

SUMMARY1. 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 secretary flux ofHCO3-and significantly reduced the absorptive flux when measured in Cl--free (SO42-) media.3. In normal media theophylline did not alter the secretary flux but significantly lowered the absorptive flux of HCO3-.4. Acetazolamide (041 mM) inhibited the theophylline-stimulated secretary flux of HCO3-and reduced the effect of theophylline on the absorptive flux.5. In normal intestine there was an inequality between the secretary or absorptive HCO3-flux and the short-circuit current (IS) consistent with the presence of Clabsorption. After addition of theophylline the ISc was more nearly equal to the net secretary 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 Clabsorption is simultaneously reduced.

Bicarbonate transport across the frog choroid plexus and its control by cyclic nucleotides.

“…640-641). Similar observations to these have been reported for the amphibian small intestine (Imon & White, 1981;Simson, Merhav & Silen, 1981a, b).…”

Chloride transport and intracellular chloride activity in the presence of theophylline in Amphiuma small intestine.

“…In summary, theophylline inhibits net Cl-absorption and also appears to stimulate HCO3secretion. In the following paper direct supportive evidence is provided for enhanced HC03secretion using the pH stat technique (Imon & White, 1981 b).…”