Simplified methods for measuring enzyme kinetics in a single cell.

We discuss techniques for measuring myeloperoxidase activity cytochemically in isolated polymorphonuclear neutrophils. We have used a sophisticated scanning microdensitometer as a reference device and compared results obtained by Zeiss Ultraphot III B and Reichert Zetopan microscopes with those of the scanning microdensitometer. We made both end-point and kinetic measurements, using conventional microscope slides and a special incubation chamber. Some resolution is lost with simpler microscope systems, but they provided results sufficiently like those obtained with the scanning microdensitometer that they could be used in the clinical laboratory to allow investigation of enzyme activity in single cells.