Regulatory Action of Estrogenic Hormones

Abstract

This chapter describes the regulatory action of estrogenic hormones. Evidence has accumulated from many sources that an initial stimulation of nuclear RNA biosynthesis triggers the subsequent biosynthetic and enzymatic events that characterize the estrogen-stimulated uterine cell. Underlying the augmented rate of RNA synthesis resulting from estrogen stimulation is increased activity of DNA-dependent RNA polymerase. Further evidence for the relationship between estrogen response by target tissues and RNA synthesis has come from the use of metabolic inhibitors. The concept that estrogens may exert their stimulatory action on the uterus by activation of RNA synthesis has been developed by several lines of biochemical investigation. In a study described in the chapter, uterine RNA obtained from estrogenized rats caused endometrial stimulation, including all the criteria usually associated with the hormonal influence, namely, transition of the lining epithelium to high columnar cells with basal nuclei and prominent nucleoli, uterine glandular proliferation, and separation of stromal cells. The activity is due to RNase-sensitive material, for there is an almost complete loss of activity when the extract is preincubated with RNase. The biological activity of RNA produced by uterine cells under estrogen stimulation suggests that estradiol, either directly or indirectly, stimulates a new pattern of RNA biosynthesis in target cells and that the hormone is not necessarily involved in subsequent steps leading to the transition from the nonstimulated to the stimulated state.