Figure 1.

Estradiol treatment of ovariectomized mice induces ductal growth and elongation in mouse mammary gland. A. Schematic of treatment strategy. Twenty-one-day old mice were ovariectomized, allowed to rest for two weeks, then exposed to either placebo or estradiol. Mammary glands were collected after two, five, seven, fourteen or twenty-eight days of treatment. Asterisks indicate the weeks represented in (B). B. (Upper panel) Whole-mounts of mammary glands from placebo or estradiol-treated mice after one or four weeks of treatment. (Lower panel) Whole-mounts of mammary glands from virgin mice at 4 and 8 weeks of age. Arrows indicate approximate origin of ductal growth. Arrowheads indicate limit of ductal growth. C. Ductal length in the mammary gland over the time course of estradiol treatment. Points represent the average ductal length measured from 3-5 mammary glands, ± SEM.