Role of RNA in the regulatory action of estrogen

Regulation of polyribosome formation and protein synthesis in the uterus. Effect of ovariectomy and administration of oestradiol-17beta on the amino acid-incorporation activity in vitro and the cytoplasmic concentration in vivo of polyribosomal preparation

1. The hormonal regulation of cytoplasmic protein synthesis in the uterus is described. Polyribosomal preparation from uteri of normal or ovariectomized rats was isolated by procedure 3 and assayed for [(14)C]leucine-incorporation activity in the cell-free system, as described by Teng & Hamilton (1967). 2. Ovariectomy of normal animals caused, 3 weeks after surgery, a 50-60% increase in the amino acid-incorporation activity in vitro of uterine polyribosomal preparation, but a 90-95% decrease in the cytoplasmic concentration in vivo of the preparation. 3. Administration of 10mug. of oestradiol-17beta to ovariectomized rats at zero time caused, 10-12hr. later, a 100% stimulation in amino acid-incorporation activity in vitro of the uterine polyribosomal preparation. From 12hr. to 36hr. after hormone administration, the activity in vitro of the preparation decreased. If a second dose of hormone was administered at 36hr., the activity in vitro of the preparation continued to decrease, and approached at 48hr. and 72hr. the lower activity observed for the preparation from normal animals. The cytoplasmic concentration of polyribosomal preparation increased by 600-700% under these experimental conditions. If a second dose of oestradiol-17beta was not administered at 36hr., the initially elevated cytoplasmic concentration of the preparation decreased by 50% from 36hr. to 72hr., and the activity in vitro of the preparation was not fully depressed to the ;normal' value. 4. Pretreatment of ovariectomized animals with actinomycin D or cycloheximide abolished 80-90% of the stimulatory effects of hormone treatment on the amino acid-incorporation activity in vitro and cytoplasmic concentration in vivo of uterine polyribosomal preparation. 5. Two major conclusions are drawn from the results reported: that during early oestrogen action new polyribosomes having amino acid-incorporation properties different from those of the old ones appear and accumulate in the cytoplasm of the uterus; and that the regulation of cytoplasmic protein synthesis in the organ by oestrogen is of an indirect nature, with dual effects of the hormone on genetic transcription resulting in turn in a regulation of the rate and amount of genetic translation.

Regional differences between nuclear concentration of (3H) estradiol and (3H) progesterone and their action on the uterus of rat during delayed implantation

The cellular and subcellular localization of radioactivity by dry-mount autoradiography was studied at 5, 15 and 30 minutes after intraluminal or at 5, 15, and 60 minutes after subcutaneous administration of (3H) estradiol or (3H) progesterone to rats in which implantation was delayed by ovariectomy on day 3 post-coitum, followed by treatment with progesterone. After intraluminal instillation of (3H) estradiol or (3H) progesterone, radioactivity was cleared from the uterine lumen at 5 minutes. After intraluminal as well as subcutaneous injection of (3H) estradiol, radioactivity was concentrated at all time intervals in the nuclei of cells of the substantia propria, glands and muscularis, but not in the luminal epithelium. White blood cells and endothelial cells were unlabeled, while perivascular cells showed concentration of radioactivity. After intraluminal instillation of (3H) progesterone, radioactivity was retained in the cytoplasm of the luminal epithelium at 5 and 15 minutes, while no such concentration appeared after subcutaneous injection. No selective nuclear retention was observed in the luminal epithelium, in contrast to the substantia propria and muscularis. The autoradiographic results indicate that progesterone treatment simulating the conditions of early pregnancy, changes the uptake affinity of uterine tissues for (3H) estradiol. The lack of a detectable concentration of estrogen within nuclei of the luminal epithelium does not preclude hormone action. Possible mechanisms of metabolic activation of the uterine luminal epithelium in the apparent absence of concentration of (3H) estradiol to nuclei of the luminal epithelium are discussed.

Induction by RNA of inositol independence in Neurospora crassa

The effect of purified wild-type RNA (allo-RNA) on genetic reversion of inositol-requiring mutant 89601 of Neurospora crassa is described. The mutant (inos minus) strain, on treatment with the wild-type RNA preparation, was found to revert to wild type (inos+) in significant numbers. RNA from the mutant (iso-RNA) and allo-RNA digested by RNase were ineffective in causing genetic reversion at the inositol locus. The allo-RNA-induced revertants were stable and showed a Mendelian transmission of the inos+ character.

Progesterone-dependent messenger RNA: heterospecific activity in vivo

The action of progesterone in mediating the synthesis of avidin by the chick oviduct can be simulated by the intraoviductal instillation of nitrocellulose-trapped RNA from hormonally prepared chick or pigeon oviduct. Similarly, the pigeon oviduct synthesizes avidin in response to chick oviduct RNA. Thus, a heterospecific transfer of hormonal stimulation, through the transfer of progesterone-induced RNA, is demonstrated. The biological activity is lost after digestion by pancreatic ribonuclease. The 50-fold purification achieved by nitrocellulose chromatography of the total RNA preparation suggests that the activity resides in a messenger RNA fraction.

Induction of avidin synthesis by RNA obtained from chick oviduct

RNA was extracted from oviduct, shell gland, and liver of chicks treated with diethylstilbestrol and a combination of diethylstilbestrol and progesterone. Preparations containing 500 or 2500 mug of RNA were put in the oviductal lumen of diethylstilbestrol-treated chicks for 24 hr, and the avidin content of the oviduct was determined by measurement of [(14)C]biotin binding. The results of the present study demonstrate that oviduct RNA from chicks treated with progesterone induces synthesis of avidin in chick oviduct. In contrast, liver or shell gland RNA from chicks treated with progesterone, and liver or oviduct RNA from chicks treated with diethylstilbestrol are incapable of inducing avidin synthesis. The inducing capacity of oviduct RNA is destroyed when it is treated with ribonuclease. It is hypothesized that progesterone induces the synthesis of new species of oviduct RNA, which serve as messenger(s) for avidin synthesis. This hypothesis is offered in consideration of the findings: (i) that the residual amount of progesterone present as a contaminant in oviduct RNA from chicks treated with progesterone is far too low to account for the induced avidin synthesis; (ii) that such oviduct RNA from chicks treated with progesterone induces a slight synthesis of avidin in chick shell gland, which ordinarily does not produce avidin in response to progesterone administration and; (iii) that such RNA added in vitro to minces of oviductal tissues incubated in biotin-free medium for 24 hr induces synthesis of avidin.

The synthesis of ribonucleic acid in immature rat uterus responding to oestradiol-17 beta

Stimulation of incorporation of labelled precursors into the RNA of immature rat uterus is an early result of oestradiol-17beta action. However, the extent of the increased incorporation varies with the mode of administration of the labelled precursors and with the weight of the rat. At the age and weight range normally used response is maximal at ten times control incorporation, 4h after the administration of 0.3mug or more of oestradiol-17beta. Under these conditions the stimulation of incorporation into the acid-soluble fraction is only 2-2.5-fold. When the purified RNA is separated on polyacrylamide gels the major increase in incorporation of radioactive precursor is found in rRNA and 4S RNA; the formation of the former has been followed from the 45S precursor. Preceding these events by at least 30min, however, is an increase in the incorporation of precursor into RNA species of very high molecular weight, which remained in the first few slices of the gel. The possible significance of these findings is discussed. The increased synthesis of rRNA in response to oestradiol-17beta is more strongly inhibited by actinomycin D than the synthesis of other RNA species. Cycloheximide, depending on time of administration and dosage, inhibits either RNA synthesis or the maturation of rRNA.

In vivo and in vitro techniques used in the study of RNA synthesis in the brains of rats and mice at various ages from birth to senility

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Partial characterization of the RNA stimulating growth of the seminal vesicle

RNA prepared from the seminal vesicles of intact adult rats, or of testosterone-treated castrate adult rats, produced a 30 per cent increase in the weight of the seminal vesicle and a 25 per cent increase in the incorporation of labeled amino acids into protein. RNA prepared from the liver or ventral prostate of the same animals produced only a 10 per cent increase in the weight of the seminal vesicle. RNA prepared from the liver of control or testosterone-treated adult female rats was ineffective in stimulating the growth of the seminal vesicle. Polyuridylic acid instilled into the lumen had no effect on the weight of the seminal vesicle, but increased the incorporation of labeled phenylalanine into protein. RNA sedimenting in the 18S area on sucrose density gradients was most effective in stimulating growth of the seminal vesicle of three-week-old rats. Treating homogenized tissue with deoxycholate greatly increased the effectiveness of the RNA extracted. RNA extracted from seminal vesicles by treatment with deoxycholate and dextran sulfate was biologically active, whereas the usual 4S RNA in the 100,000 x g supernatant is ineffective.

Steps in the reproductive process susceptible to regulation

During the past decade, family-planning programmes have been conducted on the assumption that developments in the field of contraception (e.g., hormonal contraceptives and intra-uterine devices) had reached a stage of considerable technical perfection. Enough information has now been accumulated, however, to indicate that this assumption was not fully justified; the high drop-out rates from these programmes observed under different conditions indicate that there is an urgent need for further improvements of the existing methods and for the development of new methods based on different approaches. A prerequisite for the development of such methods is a greatly improved knowledge of the physiological factors influencing the various steps of the reproductive processes in the human species.In an attempt to focus attention on the various steps which are susceptible to controlled interference, a brief review is given of some of the present concepts of the regulation of spermiogenesis, ovulation and the menstrual cycle, sperm capacitation, fertilization, tubal passage, zygote and blastocyst formation, implantation and early embryonic development. It is concluded that the reproductive processes are indeed subject to intricate biochemical and hormonal regulatory mechanisms and that the different phases of these processes do offer a variety of possibilities for hormonal, pharmacological and perhaps also immunological interference.

Ribonucleic acid: control of steroid synthesis in endocrine tissue

Ribonucleic acid extracted from either adrenal or testis altered the enzyme activity of adrenals and ovaries maintained in organ culture. The pattern of steroid hormone synthesis of the cultured endocrine tissue reflected the origin of the RNA.

Competent chick ectoderm: nonspecific response to RNA

Presumptive chick neuroectoderm responds to RNA from brain and heart by forming neural tubes, but it does not respond to liver RNA. This dif ferential response can be correlated with the presence of Folin-positive material in those RNA preparations which elicit the formation of neural structures.