Effect of sodium bicarbonate on intracellular pH under different buffering conditions

• DOI: 10.1038/ki.1996.180
• Publication Date: 2007-05-21T12:45:11Z
• Authors: Jacques Levraut; Yasser Labib; Stephane Chave; Patrick Payan; Marc Raucoules-Aime; Dominique Grimaud
• Keywords: Intracellular Fluid; Male; Buffers; Hydrogen-Ion Concentration; In Vitro Techniques; Culture Media; Rats; 3. Good health; 03 medical and health sciences; Sodium Bicarbonate; 0302 clinical medicine; Liver; Nephrology; Animals; Rats, Wistar; Acidosis

Previous in vitro studies have reported a paradoxical exacerbation of intracellular acidosis following bicarbonate therapy due to the generated CO2 entering the cytoplasm. However, these studies were conducted in nonphysiological Hepes-buffered media. We compared the effect of a sodium bicarbonate load on the intracellular pH (pHi) of hepatocytes placed in nonbicarbonate (NBBS) or bicarbonate (BBS) buffering systems. The pHi of isolated rat hepatocytes was measured using the fluorescent pH sensitive dye BCECF and a single-cell imaging technique. Cells were placed in medium buffered with HCO3-/CO2 or Hepes. All media were adjusted to pH 7 with L-lactic acid or HCl. An acute 45 mM sodium bicarbonate load was added to each medium and the changes in pHi were measured every three seconds for 90 seconds. The sodium bicarbonate load caused rapid cytoplasmic acidification of cells in NBBS (N = 50, P < 0.001). In contrast, hepatocytes in BBS underwent a marked increase in pHi (N = 50, P < 0.001) without any initial decrease in pHi. These differences were highly significant for the buffer (P < 0.01), but not for the acid used. We conclude that sodium bicarbonate exacerbates intracellular acidosis only in a NBBS. Hence, in vitro studies reporting a paradoxical intracellular acidosis following bicarbonate therapy cannot be extrapolated to the in vivo buffering conditions, and should not be used to argue against bicarbonate therapy.