OVARIAN HORMONES AND UTERINE GROWTH: EFFECTS OF ESTRADIOL, PROGESTERONE AND RELAXIN ON CELL GROWTH AND CELL DIVISION IN THE RAT UTERUS1,2

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Abstract
The influence of ovarian hormones on the uterine growth of castrated rats was studied. The effects of estradiol-17β, alone or in various combinations with progesterone and relaxin, were investigated by measuring dry weight, total amounts of pentose and deoxypentose nucleic acids per uterus and dcoxyribonuclease activity. These analyses permit a distinction between hypertrophic (increase in cell mass) and hyperplastic (increase in cell number) growth. A time-study after a single injection of estradiol showed a rather fast response as regards increase in dry weight, nucleic acid net synthesis and increase in the cellular level of deoxyribonuclease activity. These effects, however, with the exception of deoxyribonuclease activity, were of very short duration. Estradiol under these conditions induced uterine growth both by hypertrophy and by hyperplasia. Simultaneous administration of progesterone had a restrictive effect on both types of growth. Progesterone given prior to estradiol had a pronounced stimulative effect on the hyperplastic activity. Progesterone injected after estradiol exercised uterotrophic effects in terms of both cellular growth and multiplication. Relaxin in a single dose together with estradiol augmented the hypertrophic capacity of estradiol. Repeated injections of this hormone in combination with estradiol and progesterone caused both hypertrophic and hyperplastic growth. Estradiol, alone or in combination with the other ovarian hormones, caused an invariable and sometimes considerable increase in the cellular level of deoxyribonuclease activity.