Fig. 3. Total protein contents in mammary epithelial cells. Epithelial cells from four to eight fat pads were isolated, and protein was extracted as described in "Materials and Methods." By using the bicinchoninic acid protein assay kit, protein contents per 105 mammary epithelial cells were determined in each group and at each hormonal status. Numbers on the top of the columns represent the fold increase or decrease in total protein content compared with normal mammary virgin gland.