Uterine chromatin template activity during the early stages of pregnancy in the rat.

1. The template activity of chromatin prepared from rat uterine nuclei during dioestrus, oestrus and the first 7 days of pregnancy has been examined. 2. The DNA, RNA, histone and non-histone protein contents of uterine chromatin remained constant during early pregnancy. 3. The rate of RNA synthesis on Day 1 uterine chromatin was 8.61 +/- 0.59 (mean +/- S.E.) pmol of UMP incorporated/mg DNA per 10 min. When compared with DNA prepared from rat liver nuclei, 13.20 +/- 0.27% (mean +/- S.E.) of the Day 1 chromatin DNA was available for transcription by Escherichia coli RNA polymerase. 4. Uterine chromatin from rats in early dioestrus had significantly less template activity than during oestrus. 5. Chromatin prepared from whole uterus on Day 5 and from implantation sites on Days 6 and 7 of pregnancy had a significantly higher template activity than chromatin obtained from uteri on Day 1. Chromatin from interimplantation tissue on Day 6 had a lower template activity than that from uteri on Day 1. 6. RNA - DNA hybridisation of RNA transcribed from chromatin obtained on Days 2, 5 and 7 of pregnancy showed that RNA transcribed from Day 5 chromatin obtained species not present (or present in very small amounts) in RNA transcribed by chromatin from uteri on Day 2 and from implantation tissue on Day 7 of pregnancy. 7. The results are discussed in relation to the cellular changes occurring in the stroma immediately before implantation and it is postulated that the appearance of a new species of RNA on Day 5 is related to the preparation of the stromal cells for decidualisation.

Interactions of oestradiol-17beta and tamoxifen in the uterus of the pregnant rat.

Measurement of the uptake and retention of a radioactive post-coital antifertility agent tamioxifen, by reproductive tissues of the rat have shown that the ovary retained more radioactivity than did any other reproductive organ. Studies have also been made of the uptake and distribution of [3H]tamoxifen and [3H]oestradiol-17beta in the uterus of the pregnant rat on days 2-6 post coitum. Twenty-four hours after administration of tamoxifen, either i.v. or orally, 40-50% of the radioactivity was in the high speed pellet, 10-20% in the nuclear fraction, and 15-30% in the cytosol. An equivalent dose of [3H]oestradiol-17beta yielded distributions of 5%, 5% and 82% respectively. Fractionation of uteri from animals given 0-2 mg tamoxifen/kg on Day 2 of pregnancy followed by [3H]oestradiol 60 min before death showed little difference in total uptake of oestradiol or distribution in the subcellular fraction on Days 4,5 and 6. Although uptake of oestradiol by uterine nuclei was reduced on Day 3 by previous administration of tamoxifen on Day 2, appreciable quantities were still bound to the nuclear receptors. Treatment of ovariectomized animals with tamoxifen at doses up to 40 mug/rat (i.e. 0-2 mg/kg) led to the accumulation of oestrogen-receptor complex in the nucleus. It is concluded that the antifertility properties of tamoxifen (under the conditions of these experiments) cannot be ascribed to the suppression of uptake and binding of oestradiol by the uterus.

Plasma hormones and pituitary luteinizing hormone in the rat during the early stages of pregnancy and after post-coital treatment with tamoxifen (ICI 46,474).

Plasma levels of oestradiol-17beta, progesterone and luteinizing hormone (LH) and pituitary levels of LH have been measured during the first 6 days of pregnancy, in normal rats and in rats receiving two doses of Tamoxifen (trans-1-(rho-beta dimethylamino-ethoxyphenyl)-1-2-diphenylbut-1-ene) on day 2 of pregnancy. In normal rats oestradiol rose strongly from early on day 3 to reach a peak concentration between 22.00 h on day 3 and 08.00 h on day 4. Progesterone concentrations rose from day 2 to reach peak values on day 3-4. In animals in which implantation was delayed 20-24 h by administration of Tamoxifen (0.1 mg/kg) orally on day 2 the increased level of plasma oestrogen was also delayed by 20 h. A higher dose of Tamoxifen (0.2 mg/kg) on day 2, which prevented implantation, completely eliminated the increase in plasma oestradiol. Neither dose of Tamoxifen affected the levels of progesterone. In both normal rats and rats treated with 0.1 mg Tamoxifen/kg, plasma LH levels declined by day 3 while pituitary levels rose steadily. There was no detectable change in either plasma or pituitary LH levels, accompanying the increase in plasma oestradiol in the normal rats. In animals receiving Tamoxifen (0.2 mg/kg), plasma LH increased to a maximum by day 4 while levels of pituitary LH decreased. The results show that the oestrogen "surge" of early pregnancy, occurs normally about midnight on day 3 and not late on day 4 as previously thought. It is considered that the plasma oestradiol peak in early pregnancy results from an increased release of FSH rather than an increased release of LH. Tamoxifen may owe part of its antifertility action to a capacity to inhibit the synthesis of oestradiol from progesterone.

PIP: The plasma levels of estradiol-17beta, progesterone, and luteinizing hormone (LH) and pituitary levels of LH were studied in normal rats during the first 6 days of pregnancy, and in rats receiving 2 postcoital doses of Tamoxifen (trans-1-(rho-beta dimethylamino-ethoxyphenyl)-1-2 diphenylbut-1-ene) on Day 2 of pregnancy. Plasma levels of estradiol in untreated animals began to rise on Day 3 of pregnancy and reached a maximum at 20.00 hours on Day 3, before declining early on Day 4. Progesterone levels showed a similar pattern. Although progesterone levels did not vary significantly in treated animals compared to untreated animals, the highest dose of Tamoxifen eliminated the estrogen peak late on Day 3 and levels remained low up to the end of the study period. Lower doses did retard the estrogen peak, but an increase in estrogen was observed on Day 4, which was maintained until Day 6. The high dose of Tamoxifen reduced levels of pituitary LH to extremely low values, while plasma LH concentrations increased 2-3 times the concentrations found in the normal pregnant rat at Day 4. It is suggested that the plasma estradiol peak in early pregnancy is induced by a release of pituitary follicle-stimulating hormone. The antiimplantation effect of Tamoxifen may be due to its ability to inhibit the synthesis of estradiol from progesterone.

Peroxidase in human cervical mucus during the menstrual cycle.

PIP: Samples of cervical mucus were taken from 48 women not receiving oral contraceptives at different stages of their menstrual cycles. Mucus was drawn by syringe into nylon tubing of 2.8 mm external diameter, lengths cut off and sealed, and samples deep-frozen to await assay. Assay technique is described. Peroxidase was found in all assays. There were differences between individuals. A pattern of peroxidase activity could not be correlated with phases of menstrual cycles.^ieng