H(+) Current Response to CO2 and Carbonic Anhydrase Inhibition in Turtle Bladder.

摘要

To evaluate the role of CO2 and carbonic anhydrase (CA) in H(+) transport (J sub H) by turtle urinary bladder the effect of CO2 addition, with and without addition of CA inhibitors, was examined on J sub H. Since in the presence of exogenous CO2 and HCO3(-) the pH stat-measured rate of mucosal (M) acidification underestimates J sub H by the rate of electroneutral HCO3(-) secretion, the reverse short-circuit current (RSCC) applied across ouabain-treated bladders was used to estimate J sub H. The increased percent CO2 requirement for the maximum rate of J sub H with low concentrations of CA inhibitors suggests that these agents alter J sub H by decreasing the rate of enzymatic CO2 hydration. At high concentrations (acetazolamide, 5 x 10 to the -4th power M) these inhibitors decrease the maximum rate J sub H in the presence of CO2, implying that these inhibitors at higher concentrations directly interfere with the H(+) transport system.