EFFECT OF INHIBITORS OF NA+ H+-EXCHANGE AND GASTRIC H+/K+ ATPASE ON CELL-VOLUME, INTRACELLULAR PH AND MIGRATION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTES/

1 Stimulation of chemotaxis of human polymorphonuclear leucocytes (PMN s) with the chemoattractive peptide fMLP (N-formyl-Met-Leu-Phe) is par alleled by profound morphological and metabolic alterations like chang es of intracellular pH (pH(i)) and cell shape. The present study was p erformed to investigate the interrelation of cell volume (CV) regulato ry ion transport, pH(i) and migration of fMLP stimulated PMNs. 2 Addit ion of fMLP to PMNs stimulated directed migration in Boyden chamber as says and was accompanied by rapid initial intracellular acidification and cell swelling. 3 Inhibition of the Na+/H+ exchanger suppressed fML P stimulated cell migration, accelerated the intracellular acidificati on and inhibited the fMLP-induced cell swelling. 4 Step omission of ex tracellular Na+ caused intracellular acidification, which was accelera ted by subsequent addition of gastric H+/K+ ATPase inhibitor SCH 28080 , or by omission of extracellular K+ ions. In addition Na+ removal cau sed cell swelling, which was further enhanced by fMLP. 5 H+/K+ ATPase inhibitors omeprazole and SCH 28080 inhibited stimulated migration and blunted the fMLP-induced increase in CV. 6 Increasing extracellular o smolarity by addition of mannitol to the extracellular solution caused cell shrinkage followed by regulatory volume increase, partially due to activation of the Na+/H(+ )exchanger. In fMLP-stimulated cells the CV increase was counteracted by simultaneous addition of mannitol. Und er these conditions the fMLP stimulated migration was inhibited. 7 The antibacterial activity of PMNs was not modified by Hoe 694 or omepraz ole. 8 Western analysis with a monoclonal anti gastric H+/K+-ATPase be ta-subunit antibody detected a glycosylated 35 kD core protein in lysa tes of mouse and human gastric mucosa as well as in human PMNs. 9 The results indicate that fMLP leads to cell swelling of PMNs due to activ ation of the Na+/H+ exchanger and a K+-dependent H+-extruding mechanis m, presumably an H+/K+ ATPase. Inhibition of these ion transporters su ppresses the increase in CV and precludes PMNs from stimulated migrati on.