Neutrophil intracellular pH and phagocytosis after thermal trauma

Severe burn trauma induces an acquired dysfunction of neutrophil granulocyt es. As neutrophil function is considerably influenced by intracellular pH ( pH(i)), the pHi of blood neutrophils was longitudinally determined in 19 pa tients with major bums. pH(i) was measured by a flow cytometric method usin g the pH-sensitive fluoroprobe carboxy-semi-naphthorhodafluor-1; mechanisms influencing the pH(i) were examined by addition of amiloride (inhibition o f Na+/H+ countertransport), diphenylene iodonium (inhibition of NADPH oxida se) and N-formyl-methionyl-leucylphenylalanine (activation of H+ extrusion) . The neutrophil phagocytic activity was measured in parallel. Patients sho wed distinct alterations of neutrophil pH(i), depending on whether they dev eloped sepsis in the postburn period or not. In the sepsis patients pHi did not deviate from the values found in healthy volunteers in the first days after injury, but rose afterwards, with significant intracellular alkaliniz ation in the second postburn week (P < 0.05). In contrast, patients without sepsis had increased pHi in the first (P < 0.01 at days 1-2), but not in t he second week after burn trauma. Inhibition studies showed that postburn i ntracellular alkalinization is not solely caused by activation of Na+/H+ co untertransport. A clear relation between pH(i) changes and phagocytosis cou ld not be established. (C) 2000 Elsevier Science B.V. All rights reserved.