Molecular mechanisms of glial cell swelling in acidosis.

The mechanism of glial swelling in acidosis were investigated in an in vitro model. C6 glial cells were exposed to pH levels between 7.4 and 6.2. The cell volume response was determined by flow cytometry. Cell swelling of 110% to 115% was observed if pH was reduced to 6.8 or below. This effect was independent of the length of exposure to acidosis. Swelling induced by pH could be attenuated by (a) inhibition of the Na+/H+ antiporter by amiloride, (b) replacement of bicarbonate by HEPES, and (c) inhibition of carbonic anhydrase by acetazolamide. Absence of Na+ ions from the incubation medium completely prevented acidosis-induced glial swelling. Inhibition of the Cl-/HCO3- antiporter reduced swelling only in its first phase. The results suggest that glial swelling in acidosis may be from an activation of anion and cation antiporters as an attempt to maintain a normal intracellular pH. It is concluded that swelling of glial cells in the ischemic penumbra zone evolves along similar mechanisms.