A comparative study of the normal histochemical and proliferative properties of the large intestine in ICR/Ha and C57B1/Ha mice

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Abstract
The histochemical staining, labeling index and incorporation of [3H] thymidine [TdR] in large intestinal epithelium were compared in four anatomically distinct segments from ICR/Ha and C57B1/Ha mice. This comparison was done because the incidence of 1,2-dimethylhydrazine (DMH)-induced carcinomas is different for different anatomic segments as well as for the two strains. Within each strain, the amount of [3H] TdR incorporated into mucosal DNA was found to vary less than 20% at each anatomic site of the large intestine. However, there were site-specific differences in the depth of the proliferative populations within the crypts. In autoradiograms from both strains, the crypts of the proximal colon showed maximal [3H] TdR labeling of nuclei in midcrypt cells, some of which contained mucin. In contrast, the distal colon and rectum were characterized by maximal nuclear labeling in a population of undifferentiated cells near the base of each crypt. In distal ICR/ Ha colon, the proportion of labeled nuclei at each crypt depth corresponded to the [3H] TdR labeling of DNA that had been isolated from frozen sections cut sequentially. As visualized with alcian blue-periodic acid Schiff (AB-PAS) and high iron diamine-alcian blue (HID-AB) stains, the epithelial mucin showed site-specific differences, but the differences between the two strains of mice were not remarkable. In contrast to the human and rat large intestine, the acidic mucin in the mouse large intestine was predominantly sialomucin. However in the cecum and mid-distal colon, there was a predominance of sulfomucin. In the various anatomic segments of both strains, the histochemical staining, labeling index and incorporation of [3H]TdR were remarkably similar considering the large differences in susceptibility to chemically-induced neoplastic change.