In histoehemical studies of the mammary gland of rats the reaction of the enzyme activity is demonstrated during pregnancy, lactation, involution, experimental galaotostasis and under the influence of oxytocin. 38 female Sprague-Dewley rats were examined. 1st group: 7 pregnant animals, excision of tissue on the 12th, 16th, and 28th day after conception. 2nd group: 10 animals in lactation, excision of tissue on the 2nd, 10th, and 20th day after delivery. 3rd group: 7 animals on the 4th and 10th day after removing the young animals (involution). 4th group: 6 animals with experimental galactostasis on the 5th day of lactation. 5th group: 8 animals for examination of the experimental influence of oxytocin (0.5; 1.0; 2.0 IE of synthetic oxytocin per kg bodyweight i.v.). The histoehemical examination showed alcaline phosphatase (method of metallic salt and azo dye), acid phosphatase, unspecific esterase, succinic dehydrogenase, monoaminoxydase, glucose-6-phosphatase, adenosine triphosphatase, 5′-nucleotidase, glucose-6-phosphate dehydrogenase, and lactic dehydrogenase. A strong increase of the enzyme activity corresponds to the synthetic activity of the mammary gland in lactation. In comparison to lactation enzyme activity is considerably smaller in pregnancy and involution. During acute galactostasis enzyme activity decreases rapidly. Myoepithelial cells are shown by alcaline phosphatase (azo dye method) selectively. The change of the structure of these cells is demonstrated in different functional phases. In electron microscopical examination alcaline phosphatase is situated in the basement membrane and intercellular membrane and in myoepithelial cells. Also acid phosphatase and glucose-6-phosphatase can be shown in the basis of epithelial cells. Unspecific esterase-aktivity can be shown in the periphery of the lobules, in the adjacent fat tissue, and in the epithelial cells. Adenosintriphosphatase is limited to mesenchymal parts of the mammary gland. Succinic dehydrogenase, monaminoxydase, lactic dehydrogenase, and glucose-6-phosphatedehydrogenase form granulated reaction products in the epithelial cells. The results of histotopochemical examination are compared to those of biochemical examinations. © 1968 Springer-Verlag.
