Hypertonicity-induced intracellular pH changes in rat mast cells

In a non-isotonic environment, cells can shrink or swell and return to thei r normal shape by activating ion transport pathways. Changes in intracellul ar pH (pHi) after osmotic stress have been identified in several cells. In order to study the mechanisms that regulate cytosolic pH of rat mast cells in a hypertonic medium, we used the pH sensitive dye, BCECF. Under these hy pertonic conditions, pHi undergoes an alkalinization following an initial a cidification. The alkalinization is mediated by a Na+/H+ exchanger, since i t is inhibited by amiloride and lack of extracellular sodium. Under these c onditions, the alkalinization is increased with the PKC activators, TPA and GAG, and partially blocked with trifluoperazine, an unspecific protein kin ase C (PKC) and Ca+2 calmodulin-dependent protein kinases (Ca+2/CaM Ii) inh ibitor. There is also an anion exchanger, blocked with DIDS but not activat ed by PKC, that participates in the observed alkalinization. However, Na+/M + exchanger is the main mechanism involved in the alkalinization of pHi of mast cells in a hyperosmotic environment. (C) 2000 Elsevier Science Inc. Al l rights reserved.