['Neutrophils die by apoptosis, and in vivo administration of granulocyte colony-stimulating factor (G-CSF) delays this apoptotic cell death. G-CSF administered in vitro correlates delayed apoptosis with upregulation of the vacuolar proton ATPase (v-ATPase). Because this enzyme requires assembly of membrane and cytosolic domains to function, we hypothesized that in vivo G-CSF would increase synthesis and assembly of v-ATPase components to delay apoptosis.', 'Volunteers received G-CSF for 5 days, and each had a paired control. Neutrophils were isolated from subjects before the first and after the fifth injection. Proteins from cytosol or plasma membrane or from whole cell lysates were resolved by SDS-polyacrylamide gel electrophoresis and immunoblotted with antibody to the 33kDa v-ATPase E subunit. Densitometry quantified immunoreactivity.', 'No significant increase on the E subunit occurred between treated and control groups.'] Does in vivo treatment with granulocyte colony-stimulating factor delay apoptosis in human neutrophils by increasing the expression of the vacuolar proton ATPase?