NEW DYNAMIC-MODEL SYSTEM FOR THE STUDY OF CAPTURE REACTIONS FOR DIFFUSABLE COMPOUNDS IN CYTOCHEMISTRY .3. INFLUENCE OF THE MATRIX COMPOSITION ON THE LEAD PHOSPHATE PRECIPITATION PROCESS IN ACID-PHOSPHATASE CYTOCHEMISTRY

A model system for the study of the dynamics of precipitation processes, described elsewhere and consisting of polyacrylamide films, was used to investigate the influence of the composition of the matrix, in which precipitation occurs, on the lead phosphate precipitation process in acid phosphatase cytochemistry. The situation at an enzymatic site can be simulated by pumping a phosphate-containing solution and the Gomori medium for acid phosphatase (lead containing medium) along opposite sides of a polyacrylamide film. The procipitation of lead phosphate was found to start at a lower phosphate concentration of the solution flowing along films into which histone, casein, RNA or polygalacturonate had been incorporated, than in control films. DNA, chondroitin sulphate and bovine serum albumin (unfixed) did not give this effect. Fixed bovine serum albumin incorporated into the film slightly decreased the phosphate concentration at which a precipitate appeared. Nuclear staining occurring under suboptimal conditions for phosphate trapping is probably due to a local matrix effect. The model studies suggested DNA-associated phosphorylated histones and phosphoproteins as likely candidates for such an effect, and RNA as a less likely one. Artefactual precipitates at the plasma membrane might be due to carboxyl groups of sialic acid. © 1979 Chapman and Hall Ltd.