title: Response of Amphiuma small intestine to theophylline: effect on bicarbonate transport.
abstract: The electrolyte transport properties of isolated proximal segments of Amphiuma small intestine and their response to theophylline were observed under various conditions. In the absence of theophylline the intestine generates a transepithelial potential (psi ms) serosa negative to mucosa when Cl- and HCO3- are present in the bath. Replacement of Cl- or HCO3- reduced the magnitude and usually reversed the sign of psi ms. Acetazolamide (10(-4) M) nearly abolished the serosa negative psi ms. Theophylline (10 mM) drove psi ms serosa positive, the magnitude depending on the bath Na+ and HCO3- concentrations. Simultaneously it increased the short-circuit current (Isc) and tissue resistance (Rt). The increase in Isc was not due to increase net Na+ transport in Cl-free buffer and was attributed to a residual ion flux. Acetazolamide reduced the Isc, Rt, and the net residual flux observed in theophylline-treated intestine. The magnitude of the acetazolamine effect on Isc was proportional to the Na+ and HCO3- concentrations of the bath. The results suggest that in the absence of theophylline, HCO3-, and Cl- transport are related. Furthermore, acetazolamide inhibits the movement of an ion, possibly HCO3-, secreted in response to theophylline.
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D004359:Drug Therapy, Combination; D007421:Intestine, Small / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013806:Theophylline / Q000494:pharmacology*; D014562:Caudata / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D012964:Sodium; D013806:Theophylline; D000086:Acetazolamide