Effects of estrogen and progesterone on the parenchyma and blood vessels of the mammary gland in ovariectomized adult mice.

Effects of estrogen and progesterone on the first abdomino-inguinal mammary gland and associated blood vessels in ovariectomized adult mice were investigated morphometrically and by light and electron microscopy. Although there were no significant differences in the area of the mammary gland fat pad among ovariectomized groups, development of mammary parenchyma reached maximal degree in ovariectomized mice treated with estradiol (E) + progesterone (P). Epithelial cells of the mammary buds and ducts contained a small number of mitochondria and ribosomes, under-developed Golgi apparatus and rough-surfaced endoplasmic reticulum, and lipid droplets. Each organelle was more abundant in E + P treated mice than in other experimental groups. In adipose tissues of the mammary stroma in intact mice, fat cells were of a multilocular type in peripheral regions around the main vessel in the rear of the inguinal lymph node and of a unilocular type in other regions. In E and E + P treated mice, however, most of fat cells were unilocular. These findings suggest that mammary fat tissues may be formed in advance of mammary parenchyma. Blood capillaries around buds and ducts of the mammary gland were most densely distributed in E + P treated mice. Although there were no significant differences in the density of pinocytotic vesicles of endothelial cells of blood capillaries among the ovariectomized groups, marginal folds and microvillous processes reached maximal length in E + P treated mice. The diameters of blood vessels supplying the mammary gland, i.e., V. circumflexa ilium profunda and V. epigastrica caudalis superficialis, reached maximal size in ovariectomized mice treated with E + P.(ABSTRACT TRUNCATED AT 250 WORDS)