Jenfluor ap--a novel fluorogenic substrate for in situ detection of alkaline phosphatase activity

Alkaline phosphatase (AP) activity is often targeted in enzyme-related histochemistry as probe enzyme to detect neoplastic cells, as marker for primordial germ cells as well as in preimplantation studies, osteoblast differentiation, phosphate starvation in bacteria, yeast and phytoplankton. Moreover, AP-marker activity is a very useful tool in immunohistochemistry to detect gene sequences, antigens and antibodies. Here we describe a novel high resolution fluorescence method to localize AP-activity in cells and tissue sections based on a naphthol-AS azo coupling procedure (Jenfluor ap). This method provides amorphous photostable fluorescent final reaction products without any diffusion artifacts which are visible in conventional fluorescence microscopes as well as in confocal laser scanning and near infrared multiphoton laser scanning microscopes. The superiority of the Jenfluor ap method in comparison to the known Fast Red TR salt as well as the ELF stains is discussed.