Functional interaction of carbonic anhydrase and chloride/bicarbonate exchange in human platelets.
Recently, our laboratory has reported the presence of one acidifying Cl-/HC exchange mechanism in human platelets. This paper demonstrates that this exchanger decreases its activity after inhibition of carbonic anhydrase. BCECF-loaded platelets, previously equilibrated in a bicarbonate/CO2 buffered solution, were resuspended in a Hepes-buffered, chloride-free (glucuronate) medium to produce a pHi increase. After addition of 50 mM NaCl, pHi fell rapidly reaching steady state in the succeeding 400 s. The recovery in chloride-containing solution was in contrast to the effect of a similar change in osmolarity by addition of 50 mM sodium glucuronate that produced a significantly slower variation of pHi. Alkali loads produced by 25 mM TMA were also counteracted by HC equivalent efflux via Cl-/HC exchange. The present study shows that the efflux of HC was slower when the platelets were previously incubated in 100 microM methazolamide. As a conclusion, the recovery of pHi from alkalosis by Na-independent Cl-/HC exchange is facilitated in platelets by the enzymatic activity of the carbonic anhydrase.
Gende
Oscar A
OA
Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Univesidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina. ogende@atlas.med.unlp.edu.ar
D001639:Bicarbonates / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism*; D002021:Buffers; D024402:Carbonic Anhydrase II / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D006531:HEPES / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D008704:Methazolamide / Q000378:metabolism
D001639:Bicarbonates; D002021:Buffers; D002257:Carbonic Anhydrase Inhibitors; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D005456:Fluorescent Dyes; D007527:Isoenzymes; D024402:Carbonic Anhydrase II; D002256:Carbonic Anhydrases; D006531:HEPES; D008704:Methazolamide