Alkaline phosphatase for immunocytochemical labelling: problems with endogenous enzyme activity.

Area of Science:

• Biochemistry
• Histology
• Immunocytochemistry

Background:

• Alkaline phosphatase (ALP) is a widely used enzyme label in immunocytochemistry.
• Demonstration of ALP in tissue sections is typically achieved using the naphthol phosphate method.
• Endogenous ALP activity can interfere with accurate immunocytochemical staining.

Purpose of the Study:

• To evaluate methods for inhibiting endogenous alkaline phosphatase activity in tissue sections.
• To determine if inhibition methods affect immunocytochemical results when using ALP as a label.

Main Methods:

• Tissue sections were fixed using various solutions (formalin, formol alcohol, Carnoy's, Baker's).
• Endogenous alkaline phosphatase activity was inhibited using Bouin's solution or periodic acid followed by potassium borohydride.
• Immunocytochemical staining was performed using alkaline phosphatase as a label.

Main Results:

• Fixation in common solutions does not always destroy endogenous alkaline phosphatase activity.
• Bouin's solution and periodic acid/potassium borohydride effectively inhibited endogenous enzyme activity.
• The chosen inhibition methods did not adversely impact the immunocytochemical detection of the target antigen.

Conclusions:

• Proper inhibition of endogenous alkaline phosphatase is crucial for reliable immunocytochemistry.
• Bouin's solution and periodic acid/potassium borohydride are effective and compatible inhibitors.
• These findings support the use of alkaline phosphatase as a label in immunocytochemistry with appropriate inhibition protocols.