title: Chloride-induced increment in short-circuiting current of the turtle bladder. Effects of in-vivo acid-base state.
abstract: Evidence for the participation of conductive and non-conductive (exchange) transmembrane anion pathways in the luminal acidification, alkalinization, and chloride-reabsorptive functions of the turtle bladder is provided from the pattern of Cl- -induced changes in transepithelial electrical parameters of isolated urinary bladders from three groups of donor turtles: control or post-absorptive turtles (those killed 5 days after feeding); acidotic turtles (NH4Cl-loaded); and alkalotic turtles (NaHCO3-loaded). The predominance of each of the three aforementioned transport functions as well as the response to Cl- -addition is altered by the in-vivo electrolyte balance of the turtle. In post-absorptive bladders, which are poised for acidification and Cl- reabsorption, the mucosal and serosal addition of Cl- to Na+-free, (HCO3- + CO2)-containing media increases the negative short-circuiting current (Isc). In acidotic bladders, which are poised for acidification but not Cl- reabsorption, mucosal Cl- addition has no effect on this Isc whereas serosal Cl- addition increases the negative Isc in a manner identical to that observed in the post-absorptive bladders. Alkalotic bladders do not possess an acidification function but instead are poised for Cl- reabsorption and cAMP-dependent electrogenic alkali secretion (positive Isc). In these bladders, serosal Cl- addition is without effect while mucosal Cl- addition produces transient changes in this positive Isc. It is found that these results can be replicated by a model of the turtle bladder in which transmembrane Cl- and HCO3- conductive and exchange paths mediate transepithelial acidification, alkalinization and Cl- reabsorption.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000503:physiopathology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D007408:Intestinal Absorption; D013873:Thionucleotides / Q000494:pharmacology; D014426:Turtles; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine