Chloride transport and intracellular chloride activity in the presence of theophylline in Amphiuma small intestine.
1. Simultaneous bidirectional tracer fluxes of 22Na and 36Cl were measured under short-circuited conditions in isolated stripped segments of Amphiuma duodenum incubated in media containing Cl- and HCO3-. 2. Theophylline (10 mM) increased the short-circuit current (Isc), eliminated net Cl- absorption and elevated the residual flux by more than 50%. 3. Subsequent addition to acetazolamide lowered the Isc and reduced the residual flux. 4. Using double-barreled Cl- specific micro-electrodes the intracellular activity of Cl- averaged 27.1 mM in the presence of theophylline, consistent with active accumulation of Cl-. 5. Theophylline depolarized the mucosal membrane of villus epithelial cells by an average of 6.9 mV. 6. The findings indicate that the inhibition of Cl- absorption by theophylline does not result from complete inhibition of mucosal Cl- uptake and provide evidence that HCO3- secretion is enhanced by theophylline.
D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology*; D014562:Caudata / Q000502:physiology*
D002712:Chlorides; D013806:Theophylline; D000086:Acetazolamide