ISSN:
1432-2013
Keywords:
Renal proximal tubule
;
S3 segment
;
Cl−/HCO 3 − exchange
;
Carbonic anhydrase inhibitors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Cell pH (pHi) and cell membrane potential (V b) were measured in isolated S3 segments of rabbit renal proximal tubule with double-barrelled microelectrodes to search for a possible effect of the carbonic anhydrase inhibitor, acetazolamide (ACZ), on Cl−/HCO 3 − exchange in the basolateral cell membrane. ACZ was found to retard and reduce the pHi response to bath Cl− removal reversibly with half-maximal inhibition at 0.42 mmol/l and a rather flat concentration dependence (Hill coefficient ≈ 0.36). To determine whether the retardation resulted from inhibition of cytoplasmic carbonic anhydrase, which might have delayed the attainment of HCO 3 − /CO2 equilibrium, we have measured the response of pHi to step changes in PCO2 in the presence and absence of ACZ. ACZ greatly retarded the pHi response to CO2 steps; however, the concentration dependence differed (half-maximal inhibition at 18 μmol/l) and even at maximal ACZ concentrations the response to CO2 steps was more than twice as fast as the response to Cl− replacement. Since, in addition, the ACZ inhibition of Cl−/HCO 3 − exchange could not be overcome by increasing PCO2 we conclude that the ACZ effect on Cl−/HCO 3 − exchange in rabbit proximal tubule S3 segments does not result from inhibition of cytosolic or membrane-bound carbonic anhydrase, but from a direct interaction with the exchanger molecule.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00381513
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