Sucrase-
isomaltase (SI),
trehalase (T) and
lactase-
beta-glucosidase (LG) activities were assessed histochemically in samples of colorectal
adenomas (11 tubular, 12 tubulovillous, 10 villous) and 30
adenocarcinomas obtained by biopsy during colonoscopy or from specimens removed by surgical intervention. Small samples of
tumor tissue, tissue of the transitional zone and of macroscopically normal mucosa were quenched in heptan cooled in an
acetone-
dry ice mixture. Cryostat sections, transferred to non-precooled slides and in some cases to semipermeable membranes, were dried and subjected to the histochemical reactions for SI, T and LG.
Sucrose, 2-naphthyl, 6-Br-2-naphthyl, and 5-Br-4-Cl-3-indoxyl alpha-D-
glucosides,
trehalose, and 5-Br-4-Cl-3-indoxyl-beta-D-fucoside were used as substrates. Sections of jejunal biopsies with normal activities of brush border
glycosidases were used as controls. From samples of 5
adenomas, 5
adenocarcinomas and collected rests of jejunal biopsies with a normal finding 10% (w/vol) homogenates in 2%
Triton X-100 were prepared. Homogenates were frozen and thawed 3 times and their supernatants subjected to isoelectric focusing on
polyacrylamide gel plates. Zymograms were developed with the same methods as for the detection of
alpha-glucosidases in sections. In no
colorectal tumor LG was present. SI was found in 70%
adenocarcinomas, 50% villous, 25% tubulovillous and 19% tubular
adenomas when the method with
sucrose,
glucose oxidase-
peroxidase and
3,3'-diaminobenzidine was used. Hardly discernible traces of activity were found in
tumors with azo-coupling reactions applied at pH 5, 6 and 6.5. No reaction was detected with the indigogenic method applied at pH above 6.0. However, jejunal biopsies displayed very strong reactions confined to the brush border of enterocytes under the same conditions. A strongly positive reaction was seen in 7 of 12
tumors investigated recently when the indigogenic reaction was applied at pH below 6.0 (particularly at pH 5.0). In this case the deposition of
indigo was due to membrane and lysosomal
alpha-glucosidases of the
tumor cells and
lysosomal alpha-glucosidase of macrophages and leukocytes. These findings were corroborated by zymograms. T was detected in the same
tumors as SI; its activity was lower, however. SI activity in
colorectal tumors is a useful, but not general marker of these
tumors.