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Cl/HCO3 antiport affects H-lactate symport activity at the basolateral pole of jejunum enterocyte
A Faelli1, M N Orsenigo, A Verri
1Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italia. afaelli@imiucca.csi.unimi.it
Background/Aims:
Under normal conditions the jejunal tract of the rat intestine absorbs HCO3. A basolateral Cl/HCO3 exchange, evidenced by means of membrane vesicles, could be involved in this process. Aim of this study was to investigate the anion exchange activity in the whole jejunal tract, where various transport systems could interact.
Methods:
In the jejunal tract of rat intestine everted and incubated in vitro, the experimental conditions set up minimized loss of CO2 from the serosal solution, where pH and pCO2 were determined together with fluid and electrolyte transintestinal transport.
Results:
The serosal pCO2 increase and pH decrease, evident during the experiment, could be antagonized by enhancing the 4,4-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) concentrations in the serosal fluid. Moreover high DIDS concentration affected fluid, sodium, lactate, bicarbonate and, although in the opposite direction, chloride transport, whilst they were ineffective on K flux.
Conclusion:
These results give evidence that in the basolateral membrane the inhibition of Cl/HCO3 antiport causes a diminution of lactic acid movement. Therefore we can hypothesize that Cl/HCO3 antiport facilitates basolateral H-lactate symport in order to carry endogenous lactic acid towards the blood stream.