Characterization of the Na+/HCO3 - Cotransport in Human Neutrophils

Abstract

Background: Bicarbonate transport has crucial roles in regulating intracellular pH (pHi ) in a variety of cells. The purpose of this study was to evaluate its participation in the regulation of pHi in resting and stimulated human neutrophils. Methods: Freshly isolated human neutrophils acidified by an ammonium prepulse were used in this study. Results: We demonstrated that resting neutrophils have a bicarbonate transport mechanism that prevents acidification when the Na+/H+ exchanger is blocked by EIPA. Neutrophils acidified by an ammonium prepulse showed an EIPA-resistant recovery of pHi that was inhibited by the blocker of the anionic transporters SITS or the Na+/HCO3 - cotransporter (NBC) selective inhibitor S0859, and abolished when sodium was removed from the extracellular medium. In western blot and RTPCR analysis the expression of NBCe2 but not NBCe1 or NBCn1 was detected in neutrophils Acidified neutrophils increased the EIPA-insensitive pHi recovery rate when its activity was stimulated with fMLF/ cytochalasin B. This increase in the removal of acid equivalents was insensitive to the blockade of the NADPH oxidase with DPI. Conclusion: It is concluded that neutrophils have an NBC that regulates basal pHi and is modulated by chemotactic agents.