Effects of Estrogen on Mitosis in Individual Cell Types of the Immature Rat Uterus1

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Abstract
This study was initiated to determine the time course of estrogen action in individual uterine cell types of the immature rat uterus. Animals were treated with a single injection of estradiol-17β for various times and colchicine was administered 4 h prior to sacrifice. In the luminal epithelium, a peak of arrested mitoses was observed 24 h after hormone administration and represented ∼12% of the cell population. In contrast both the stroma and myometrium displayed a peak of arrested mitoses 36-48 h after hormone administration and the maximum value represented ∼1% of the total cell populations. These results indicate that the patterns of estrogen-induced cell division are quantitatively and qualitatively distinct in the different cell types of the immature rat uterus.