Enzyme-incorporated erythrocyte ghosts: a new model system for quantitative enzyme cytochemistry

The preparation and properties of a new microscopic model system for quantitative enzyme cytochemistry are described. The enzyme to be studied is entrapped in human erythrocyte ghosts by a simple hypotonic procedure. After fixation in suspension the ghosts can be analyzed both biochemically and cytochemically. The system has been tested with alkaline phosphatase. It is demonstrated that an azo method that uses naphthol AS-MX phosphate as substrate and 4-aminodiphenylamine diazonium salt as coupling agent can detect very low levels of enzymic activity. The biochemical activity determinations of alkaline phosphatase loaded erythrocyte ghosts were found to correlate linearly with cytophotometric activity determinations. The possible use of the erythrocyte ghost model system for other cytochemical applications is briefly discussed.