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SUMMARY
A method is described for the isolation of a purified luteinizing hormone (LH) from the anterior lobes of porcine pituitary glands. This includes fractional precipitation, gel filtration and isoelectric focusing. The preparation, which can be recovered in a fairly short time, is of high potency (equivalent to 3·4 mg standard NIH-LH-B7/mg and 6800 i.u. LH/mg).
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SUMMARY
Plasma levels of oestradiol-17β, 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-(p-β 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.
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Search for other papers by A. P. F. FLINT in
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Search for other papers by A. C. TURNBULL in
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SUMMARY
Maternal plasma progesterone levels in sheep may fall dramatically during the last few days of gestation and following the administration of glucocorticoids to the foetus. To investigate the mechanism of the fall, metabolism of [3H]pregnenolone and/or [3H]progesterone in vitro by ovine placental tissue was studied in five ewes before and after intra-foetal administration of dexamethasone in a dosage sufficient to induce parturition, and in one ewe after the spontaneous onset of labour at 143 days of gestation. Manual separation of maternal and foetal placental tissues showed that, in 11 out of 12 cases, the foetal and not the maternal placenta produced progesterone from pregnenolone in vitro. Total activities of cholesterol side-chain cleavage enzyme and 3β-hydroxysteroid dehydrogenase in the foetal placenta were not influenced by intra-foetal dexamethasone. Before administration of dexamethasone, homogenates of foetal placenta converted [3H]progesterone to 20α-hydroxy [3H]pregn-4-en3-one in the presence of NADPH. Within 12 h of administration of dexamethasone, and after the natural onset of labour at 143 days, large amounts of 17α,20α-dihydroxy[3H]pregn4-en-3-one were formed from [3H]progesterone. Intra-foetal dexamethasone treatment also induced the formation of 17α,20α-dihydroxy[3H]pregn-4-en-3-one by minced foetal placental tissue incubated with [3H]pregnenolone. This change in steroid metabolism did not occur in foetal placental tissue from a sham-operated animal receiving no dexamethasone. Assay of progesterone in foetal placentae showed that the increased formation of 17α,20αdihydroxypregn-4-en-3-one was unlikely to be caused by a change in the specific activity of added 3H-labelled precursor, although the production of 17α,20α-dihydroxypregn-4-en3-one in vitro increased at a time when both foetal placental and utero-ovarian venous levels of progesterone were decreasing in response to dexamethasone treatment. These observations indicate that intra-foetal dexamethasone treatment induces a placental 17α-hydroxylase enzyme, which is also present in foetal placental tissue after the spontaneous onset of labour at term.
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Search for other papers by A. C. TURNBULL in
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SUMMARY
Simultaneous measurements of prostaglandin F, total unconjugated oestrogens and progesterone have been made in utero-ovarian venous or posterior vena caval plasma from pregnant ewes during parturition. In all cases, levels of oestrogens and prostaglandin F increased before delivery, after a decrease in the level of progesterone. In four out of six sheep, during both spontaneous and dexamethasone-induced labour, increases in the levels of oestrogens and prostaglandin F occurred in parallel. In the other two animals, levels of prostaglandin F increased before those of oestrogens. The increases in prostaglandin F consistently preceded any measurable increase in uterine activity, suggesting levels were not raised as a consequence of labour. Infusion of oestrogen to two dexamethasone-treated animals resulted in increased utero-ovarian venous prostaglandin F levels within 2–3 h. These findings support previous evidence indicating that levels of prostaglandin F may be controlled by oestrogen and progesterone. Manual examination of the cervix, with associated distension of the vagina, resulted in dramatic increases in the level of utero-ovarian venous prostaglandin F during the last 13 h of gestation, both in dexamethasone-induced labour and in labour of natural onset. Since expulsion of the foetus also results in vaginal distension, this finding raises the possibility that the very high levels of prostaglandin F observed at delivery may be caused by tactile stimulation of the vagina.
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Nuffield Department of Obstetrics and Gynaecology, John Radcliffe Hospital, Headington, Oxford, 0X3 9DU
(Received 24 April 1974)
Progesterone levels in the blood of pregnant sheep increase with increasing number of foetuses and with gestational age (Bassett, Oxborrow, Smith & Thorburn, 1969), and are thought to be reduced as a result of foetal cortisol secretion preceding parturition (Liggins, 1973). Data presented here suggest that β-adrenergic stimulation may also influence placental progesterone production.
Utero-ovarian venous and intra-amniotic catheters were inserted in four pregnant ewes, gestational ages 119–130 days, 3–4 days before experimentation. Jugular venous catheters were inserted on the day of the experiment, which was carried out on the conscious animals. Progesterone, total unconjugated oestrogens (oestrone + oestradiol-17/β + oestradiol-17α) and prostaglandin F were measured in utero-ovarian or jugular venous plasma by specific radioimmunoassays (Flint, Anderson, Patten & Turnbull, 1974). Neither orciprenaline nor salmefamol cross-reacted at concentrations up to the equivalent of
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Search for other papers by PENELOPE A. STEELE in
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Search for other papers by A. C. TURNBULL in
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SUMMARY
Progesterone, 17α,20α-dihydroxypregn-4-en-3-one, androstenedione, total unconjugated oestrogen and oestrone sulphate have been measured by radioimmunoassays in maternal utero-ovarian venous, maternal peripheral venous and/or foetal posterior vena caval plasma from six sheep bearing bilaterally adrenalectomized lambs, in which premature parturition was induced by administration of glucocorticoid. Three of the ewes were ovariectomized, and in one of these three animals the foetal testes were also excised, at the time of foetal adrenalectomy. Adrenalectomy was judged to be complete on the basis of plasma cortisol levels in the neonatal lambs, and by examination of the site of ablation at necropsy. In all cases foetal administration of glucocorticoid led to the onset of labour, and lambing, and in all animals the hormonal changes preceding parturition were indistinguishable (either qualitatively or quantitatively) from the changes observed in animals carrying intact lambs. Since therapy with glucocorticoid alone successfully compensates for ablation of the foetal adrenal cortex, it is suggested that glucocorticoid is the only adrenal product required to cause parturition, and that foetal adrenal secretion of androgens may be unnecessary.
