Intracellular pH regulation in cultured microglial cells from mouse brain

Abstract

Intracellular pH (pH1) and the mechanisms of pH1 regulation have been investigated in cultured microglial cells from mouse brain using the pH‐sensitive fluorescent dye 2′,7′‐bis‐(2‐carboxyethyl)‐5‐(6)‐carboxyfluorescein (BCECF). Cells were acidified by a pulse of NH4+ (4‐5 min; 20 mM) and the subsequent pH1 recovery from an acidification was studied. In HCO3‐‐free saline, pH regulation was dependent on extracellular [Na+] and sensitive to amiloride, indicating the involvement of the Na+/H+ exchanger. In HCO3‐‐containing solution 2 mM amiloride slowed but did not block pH1 recovery; the recovery however was dependent on extracellular [Na+] and sensitive to 0.3 mM DIDS, suggesting the presence of Na+/HCO3 cotransporter and/or Na+‐dependent Cl‐/HCO3‐ exchanger. The involvement of a Na‐dependent Cl‐/HCO3‐ exchanger was inferred from the observation that removal of Cl‐ or application of 1 mM furosemide decreased but did not block the recovery rate. Increasing [K+]0 resulted in an alkalinization by a process that was neither HCO3‐ nor Na+‐dependent, nor DIDS‐ and amiloride‐inhibitable. In conclusion, microglial cells express a distinct set of pH regulatory carriers which control for a defined level of pH1. An increase in [K+]0 can offset this level. © 1996 Wiley‐Liss, Inc.

Activation of Microglia Depends on Na+/H+Exchange-Mediated H+Homeostasis

“…To our knowledge, there is only one report suggesting Na + /H + exchanger is involved in pH i recovery after intracellular acidosis in mouse primary microglia (Faff et al, 1996), using the non-selective NHE inhibitors amiloride or EIPA. These inhibitors may block other Na + -dependent transporters or channels (Murphy and Allen, 2009).…”

Physiology of Microglia

“…The presence of operational Na ϩ /HCO 3 Ϫ cotransporter and/or Na ϩ -dependent Cl Ϫ /HCO 3 Ϫ exchanger was found in cultured microglia (260). Anion exchange-mediated chloride/bicarbonate transporter is a major component in the regulation of intracellular pH.…”

Quantitating the subtleties of microglial morphology with fractal analysis

“…This result was attributed to a technical issue that rendered secondary branches invisible on many of the ramified cells (Karperien, 2004). The cytoskeletal reorganization seen in microglia is known to distinguish microglial ramification from ramification of other cells, so it might be informative to separate cytoskeletal rearrangements from strictly membrane features (Faff et al, 1996; Tanaka et al, 1999; Faff and Nolte, 2000; Ohsawa et al, 2000). Perhaps comparing cytoskeletal components in cultured and in vivo microglia would eliminate the difference, or perhaps the difference is indeed inherent to the spatial context of microglia in the culture environment.…”