Ultrastructural Description of three Different Epithelial Cell Types in Rat Mammary Gland.

Abstract

The mammary gland is composed of epithelial and myoepithelial cells. In the present work, we show that the epithelial component is composed of three types of cells differing in their ultrastructural profiles.Sprague-Dawley virgin female rats, 60 to 100 days old, were sacrificed during estrus. The mammary gland was fixed in Karnovsky's fluid (1), embedded in Epon-Araldite (2), thin-sectioned, stained with uranyl acetate and lead citrate, and examined in an Hitachi HU-11A or a Siemens Elmiskop 1A. To see whether ultrastructural differences correspond to size differences, the nuclear and cytoplasmic areas of 1000 cells were determined from photographs at 10,000X, using a compensating polar planimeter.The population of epithelial cells in the mammary gland is comprised of three different cell types (Fig. 1): a) light cells, b) dark cells, and c) intermediate cells.