Role of RNA in the regulatory action of estrogen.

Abstract

Estrogens, as well as other steroid hormones, may exert their stimulatory effect on target tissues by initial activation of RNA synthesis. 1 2 This concept is supported by the observation that estrogen stimulation of the uterus leads quickly to an increase in the rate of incorporation of precursors into RNA,3 4 the initial increase being noted in the nuclear fraction of RNA.5 The uterotrophic action of estradiol-17f3 is prevented by the metabolic inhibitor actinomycin D either administered systemically6 or by injection into the lumen of the uterus.7 The action of estrogen on the vagina can be prevented also by topical application of actinomycin.5 A mechanism for the effect of estradiol on RNA synthesis has been suggested by the identification of a macromolecular fraction of the cell which possesses receptors for the hormone. This fraction, when not combined with the hormone, inhibits the activity of RNA polymerase. When the hormone is present, the inhibition is released.9 The biochemical evidence that the biosynthesis of RNA by rat uteri is immediately accelerated by estrogen suggests that the stimulating hormone may have no further role in causing the transition from the atrophic to the stimulated state. To test this postulate, RNA was extracted from the uteri of estrogen-stimulated rats and administered by local, intraluminal application to estrogen-deprived ovariectomized rats. The resultant morphologic changes in treated uteri are indistinguishable from those that occur following the administration of estrogen.10 Materials and Methods.-Preparation of total RNA extract: Method A: Female rats of the Sprague-Dawley strain weighing 180-200 gm were ovariectomized, and the certainty of anestrus was established by following the vaginal smears for at least two weeks. Each batch of RNA was prepared from the uteri of at least ten ovariectomized females but frequently as many as 100 were used. Each animal was injected intravenously (tail vein) with 10 jsg estradiol-17,3 per 1 ml 1% ethyl alcohol in saline. After 4 hr, the animals were sacrificed by decapitation; the uteri were removed and quickly frozen. In the 4°C cold room, the uteri were homogenized with a Virtis homogenizer in 10 times volume of saline, with or without 0.001 M MgCl2. The tissue brei was filtered through one layer of cheesecloth and mixed with an equal volume of watersaturated phenol. The mixture was stirred vigorously on a magnetic stirrer for 30 min at room temperature, and the stirring was repeated for 30 min in the 4°C cold room. It was centrifuged at 2,000 gravities for 30-60 min at 2-4°C, and the top aqueous layer was saved. The other layers were washed once with an equal volume of saline, centrifugation was repeated, and the saline was combined with the original supernatant with extreme care to avoid carrying over any saline-Downloaded by guest on July 4, 2020

Hormonal Regulation of the Reproductive Tract in Female Mammals

“…The RNA extract initiated morphological changes in the endometrium that were characteristic of estradiol stimulation. Saline, vagina, or liver RNA prepared from estradiol stimulated rats, uterine RNA prepared from nonstimulated rats, and RNase-treated uterine RNA (prepared from estradiol-stimulated rats) failed to cause the estrogen effect in the control horn of the same rat (169). The stimulatory uterine RNA extracts were not contaminated with enough estradiol to account for the effect.…”

“…The stimulatory uterine RNA extracts were not contaminated with enough estradiol to account for the effect. Actinomycin D treatment does not block the cellular hypertrophy induced by active RNA extracts (169 (116) demonstrated that when RNA prepared from the uteri of mature cycling mice was administered by intrauterine injection to spayed mice, the biosyn thesis of alkaline phosphatase was increased and the normal adult appearance of the endometrium was restored. The ability of RNAs from bovine ovary and uterus to stimulate the local response and to increase mouse uterine ,a-glucuronidase activity was reported in a later study (114).…”

Intraoviductal Administration of Ribonucleic Acid from Estrogen-Treated Rats Mimics the Effect of Estrogen on Ovum Transport1

“…A literature search revealed very few reports in which this approach was claimed to work [7][8][9]. Moreover, recent reports indicate that oligonucleotides do enter cells and affect their function [10,11].…”

Induction by RNA of inositol independence in Neurospora crassa.

“…The transfer of other genetic characters mediated by purified RNA preparations has also been reported (5, 6). In higher organisms the development of specifictissues in response to exogenous RNA during organ culture has been described (7,8). The possible role of RNA in transfer of genetic information is supported by the discovery of the enzyme, reverse transcriptase (RNA-dependent DNA polymerase) (9, 10), which can transcribe an RNA template into DNA.…”