Freeze-preservation of staining solutions in enzyme histochemistry.

Staining solutions of acid phosphatase and esterase group (naphthol-AS-D-chloroacetate esterase, naphthol-AS-acetate esterase and alpha-naphthyl-acetate esterase) were stored for 6 months using the freezing facilities, and the staining results were compared with those of each set of controls. The results showed that the staining solutions of all enzymes were stable for long-term preservation (at least 6 months) in the deep freezer (-80 degrees C) when they were stored appropriately in separated forms. In such a freezing procedure, the staining results for each enzyme did not show any decrease of positive intensity nor any non-specific staining.