5-Bromo-2-deoxyuridine labeling indices in mammary glands of PR-A transgenic mice under various hormonal statuses. Percentage of 5-bromo-2-deoxyuridine (BrdU)-positive mammary epithelial cells of normal ducts (ND) and hyperplastic ducts (HD) of PR-A transgenics under various hormonal statuses. Data presented as the mean ± standard error of the mean. Mammary glands from a minimum of three mice were examined, and mammary glands for each mouse were analyzed in triplicate. In each experiment, the percentage of immunopositive cells was obtained by counting a minimum of 500 cells per gland. Ovx, ovariectomized mouse; Ovx+E, ovariectomized mouse treated with estradiol 1 μg.