Dehydrogenases in Local Carcinogenesis in Rat Mammary Gland by Dusting of Dmba-Powder

Abstract

To the 5th right mammary gland of Sprague-Dawley female rats, ca 1 mg of DMBA was directly administered by means of a dusting of its pure powder over the mammary fatty pad. At the site of administration, a nodule of adenocarcinoma was induced more than 7 weeks after the local application with high incidence.It was enhanced more in the adults than the youngs. Histochemically, atypisms of ALP and LDH activities were observed on the apparent malignant tissues induced by DMBA-dusting. Biochemical observations on the activities of LDH and MDH and on the pattern of LDH isoenzymes were done for the induced nodules with DMBA-dusting over females aged 8-26 weeks, which were harvested 5-18 weeks after the local application. The quotients of LDH/MDH in the same sample elevated on the malignant tissues prominently owing to higher LDH activity, and the elevation was moderate on the earlier-harvested, granulomatous tissues. But, the shift toward predominance of the M type of LDH was detected distinctly in the earlier granulomatous samples harvested 5 weeks after the local application.Mammary tissues of the rat are foremost among cells of mammals in terms of susceptibility to the induction to cancer by 7,12-dimethylbenz (a) anthracene (DM BA). Mammary adenocarcinoma rapidly becomes evident in young adult SpragueDawley females administered with a pulse dose (6). But the site of initiation and early changes of carcinogenesis cannot be pointed out so soon in experiments of such systemic administration.Shinha and Dao (17) developed a technique for inducing mammary tumors by direct application of a minute quantity of DMBA. The location of early carcinogenesis might be indicated immediately after the administration of carcinogen in this experimental design. In the present paper, the mammary tumorigenesis by local application of DMBA into females aged 6-26 weeks was observed histopathologically, and then histo-and bio-chemical observations on some enzymic activities were serially done in the carcinogenesis with DMBA-dusting over the mammary fatty pads of adult females, in comparison with control mammary fatty pads, spontaneously occurring mammary fibroadenomas and induced mammary adenocarcinomas with pulse doses of DMBA.

Histochemical observations on enzymes in pregnancy-dependent mammary tumors of GRS/A mice.

“…In general, LDH became stronger in many malignant tumor cells in GR mammary tumorigenesis. The deviation of LDH isoenzyme patterns should be studied in the tumor progression of GR mice, as well as human and rat mammary tumors (19).…”