Fluorescence methods for localizing proteinases and proteinase inhibitors in skeletal muscle

Proteinases and proteinase inhibitors have become suspect in a wide variety of muscle wasting conditions that might be treatable if knowledge of the cellular locale and function of these molecules were known. Fluorescent probes have been useful in the localization of proteinases in muscle samples from human and animal specimens. These include the histochemical localization of proteinases based on the specific fluorescence of hydrolysis product derivatives, but this approach has been limited to the lysosomal proteinases because of the acidic requirements of the trapping reaction of the primary reaction product. Immunohistochemical techniques do not have the same restrictions and a number of lysosomal and nonlysosomal proteinases have been identified in muscle by this means. Unfortunately, they do not yield any information as to the activity of the enzymes. This is an important consideration since the extracellular environment contains a number of proteinase inhibitors, some of which may be internalized by the cell.