Lactic acid-induced swelling in C6 glial cells via Na+/H+ exchange.
Paraules clau
Resum
One of the primary consequences of ischemia is tissue acidification due to anaerobic production of lactic acid. Upon reperfusion and recovery of pH, cytotoxic edema often ensues. Na+/H+ exchange, a mechanism involved in the regulation of intracellular pH (pHi), is activated by low intracellular pH, is dependent on extracellular Na+, and is inhibited by low extracellular pH (pH less than 6) or by amiloride. In this study we explore the role of Na+/H+ exchange in cell swelling following cytoplasmic acidification of C6 glioma cells. Postischemic intracellular acidification was simulated in vitro by exposure of cells in suspension to: (1) 20 or 140 mM lactic acid; or (2) 10 microM oligomycin. pHi was monitored fluorimetrically using the intracellularly trapped pH-sensitive dye bis(carboxyethyl)carboxyfluorescein. Cell volume was measured electronically with a Coulter Counter/Channelyzer. Both simulations of ischemia caused intracellular acidification followed by recovery. pHi recovery was mediated by Na+/H+ exchange, since it was amiloride-sensitive and Na+-dependent. This pHi reversal following lactic acid-induced acidification was also inhibited at pHo less than 6. Volume measurements showed that cells suspended in 140 mM Na-lactate/lactic acid swelled by 19% over 15 min. This swelling was Na+-dependent, and inhibited by amiloride and pHo less than 6. These results suggest that Na+/H+ exchange may be involved in cell swelling following cytoplasmic acidification, and thus may be involved in postischemic cytotoxic brain edema.