2 TYPES OF PUTATIVE PRENEOPLASTIC LESIONS IDENTIFIED BY HEXOSAMINIDASE ACTIVITY IN WHOLE-MOUNTS OF COLONS FROM F344 RATS TREATED WITH CARCINOGEN

Previous studies identified as putative preneoplastic lesions 1) enzym e-altered foci in sections of methacrylate-embedded colon and 2) aberr ant crypts in methylene blue-stained unembedded (whole-mount) colon an d established that aberrant crypts embedded in methacrylate bad enzyme alterations. We have now studied histochemically demonstrable hexosam inidase activity in unembedded or whole-mount preparations of colons f rom carcinogen-treated rats. These preparations have revealed two popu lations of crypts that are enzyme-altered: those that are morphologica lly altered or aberrant and those that are morphologically normal. Bot h populations can be quantified rigorously in less than an hour with w hole-mount preparations reacted for hexosaminidase. The demonstration of phenotypic characteristics with histochemical techniques in whole-m ount preparations should have wide applicability to functional studies in many normal and diseased tissues.