Comparison of Fixatives and Substrates for Aminopeptidase

Although aminopeptidase activity is extensively inhibited by glutaraldehyde, it is sufficiently well preserved after brief glutaraldehyde fixation for histochemical use in active tissues in contrast to the too great losses with comparable formaldehyde-fixation. The localization of histochemical activity is sharper with glutaraldehyde-fixed frozen sections than with fresh frozen sections in many tissues though not all, and both methods are better than with formalin fixed tissue. Comparison of the results with leucyl, methionyl and alanyl amides of the rapid coupler, 4-methoxy-2-naphthylamine, showed exactly the same localization.