in Situ Histological Evaluation of Elastase Activity

A simple technique is described for demonstrating the relative extent of elastin digestion produced by various enzymes in salt-cured but otherwise intact tissue. Pieces of steer hide, or similar material, are incubated with strong solutions of enzyme at 38°C for 7 or 17 hr, washed and fixed with formalin. Frozen sections (30 to 40μ) are cut perpendicular to the skin surface, stained for elastin by the Verhoeff and by the Fullmer-Lillie methods, and mounted on slides. Microscopic examination within the zone of dense elastin is directed at determining the transition point above which the fibers have been visibly altered, but remain unchanged below. The depth of this point is expressed as percent of total depth of dense elastin to provide a numerical value for elastase activity. Such values have been obtained for papain and trypsin, as well as several other enzymes currently under investigation for use as unhairing agents.