Comparative study of assays for stimulated fluid pinocytosis in canine and human neutrophils

We compared a flow cytometric assay of fluid pinocytosis in stimulated neutrophils with previously used methods, including spectrophotofluorometric assay of fluoresceinated dextran (FD) uptake and beta scintillation spectroscopic assay of radiolabeled sucrose uptake. Neutrophils from human and canine blood were stimulated with formyl-methionyl-leucyl-phenylalanine and phorbol myristate acetate, respectively. Flow cytometry was used to quantitate uptake of FD and lucifer yellow, spectrophotometry was used to quantitate uptake of FD, and spectroscopy was used to quantitate uptake of 14C-labeled sucrose. The flow cytometric assay, using either FD or lucifer yellow, was found to be superior on the basis of maximal incremental increase observed, minimal variability within replicate experiments, and maximal sensitivity to detect early stimulation of fluid pinocytosis in neutrophils.