It is well known that chemotactic agents active Na+/H+ exchanger, increasing intracellular pH of neutro-phils, but their effect on bicarbonate transporters have not been established yet. To study the effect of fMLP on the activity of Cl-/HCO3- exchange, the rate of pH recovery after acute Cl- readmission in cell subjected to an alkaline load by CO2 washout in a Cl-free medium was measured. The activity of the exchanger was reduced to 72% of control when cells were pre-incubated for 5 min with 0.1 mu M fMLP and reached 48% of control in steady state after acute exposure. After extracellular bicarbonate or TMA addition the rate recovery of intracellular pH was reduce at 72% and at 84%, respectively. The inhibitory effect on the intracellular pH recovery was not affected by blockers of Na+/H+ exchange. We conclude from these studies that an increase of pH(i) produced for this chemotactic agent is facilitated by the simultaneous activation of Na+/H+ exchange and inhibition of Cl-/HCO3- exchange in neutrophils. (C) 2011 Elsevier Inc. All rights reserved.