Cytochemical model system for microsomal rat liver glucose-6-phosphate.

A method is described for the incorporation of a microsomal rat liver fraction into polyacrylamide films without significant loss of its glucose-6-phosphatase activity. The enzymatic activity was completely lost when the films were prepared with ammonium persulfate as initiator of the polymerization as previously described for alkaline phosphatase, but modification of this method showed that about 90% of the glucose-6-phosphatase activity could be retained. The enzyme in the films prepared with the new method was completely inhibited by alloxan, HgCl2, and preincubation in 0.05 M acetate buffer (pH 5.0) at 37 degrees C, as determined biochemically. Similar results were obtained for the enzyme in films determined histochemically according to the lead method of Wachstein and Meisel. In this respect the behavior of the incorporated enzyme is similar to that in suspension. Films fixed with 1.5% glutaraldehyde showed rapid inactivation of glucose-6-phosphatase. There was good correlation between the biochemical and histochemical activity determined after fixation. A method to embed polyacrylamide films in Epon for electron-microscopical investigation is also described. Dimethyl sulfoxide was used as the dehydrating agent instead of ethanol/acetone.