Fluorescence of eosinophil leukocyte granules induced by the fluorogenic reagent 2-methoxy-2,4-diphenyl-3 (2H)-furanone.

The fluorogenic reagent MDPF forms highly fluorescent products specifically with primary amino groups (e.g., from lysine). Although widely used in analytical biochemistry, MDPF has infrequently been employed in cytochemical techniques for proteins. In this work, we describe the application of MDPF in fluorescence microscopy studies of horse, rat, and human blood cells. Under ultraviolet excitation, MDPF selectively induces an intense white-blue fluorescence reaction in the granules of eosinophil leukocytes, which contain strongly basic proteins. The advantages of MDPF for identification to reveal protein components in hematological cytochemistry are briefly discussed.