Ultrastructural changes in fat cells and blood capillaries of the mammary gland in starved mice.

The effects of starvation on fat cells and blood capillaries of the first abdomino-inguinal mammary gland in mice were investigated by light and transmission electron microscopy. The body weight of starved mice abruptly decreased to approximately 70% of that of controls at 3 days of starvation and, thereafter, gradually decreased. In adipose tissues of mammary stroma, multilocular fat cells increased in number and clustered during starvation to a glandular appearance at 6 days. Collagen fibers increased in amount around mammary ducts and buds. By electron microscopy, multilocular fat cells possessed numerous mitochondria, small lipid droplets, and plasmalemmal vesicles, while endothelial cells of the blood capillaries showed numerous pinocytotic vesicles plus short marginal folds and microvillous processes. These observations prove that the number of pinocytotic vesicles in blood capillary endothelium is closely related with the increased amount of lipid of fat cells in the mammary gland during starvation.