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MARGARET RYLE, JENNIFER COURT, TERESA SMITH and R. MORRIS

SUMMARY

The amount of oestrogen produced by immature mouse ovaries cultured with purified gonadotrophins was measured by means of a radioimmunoassay. Small quantities were released in response to FSH or LH alone, but when both were provided production was greatly enhanced after an initial lag phase of 2–3 days. The lowest concentrations required to produce this synergistic effect were between 0·02 and 0·13 i.u. FSH/ml and between 0·01 and 0·1 i.u. LH/ml. After prolonged exposure to 0·4 i.u. FSH/ml plus 1·0 i.u. LH/ml, oestrogen output continued to rise until, on the ninth day of culture, it reached 2·6–7·3 ng/ ovary/day. Pre-treatment with 0·4 i.u. FSH/ml for 3 days enhanced the subsequent response to combined gonadotrophins but the simultaneous presence of FSH and LH was essential for inducing the delayed synergistic effect. Although both gonadotrophins also stimulated follicle growth there was no evidence suggesting any simple correlation between that response and oestrogen synthesis. Maximal oestrogen production coincided with very low follicular mitotic activity.

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P. W. NATHANIELSZ, MARGARET ABEL and G. W. SMITH

Prostaglandin F (PGF) has been shown to possess luteolytic properties in several species including the rabbit (Duncan & Pharriss, 1970; O'Grady, Kohorn, Glass, Caldwell, Brock & Speroff, 1972). Surgical removal of the corpus luteum leads to parturition in the rabbit. Thus, PGF should initiate parturition in this species. In primates, controversy has arisen over the ability of PGF to produce luteolysis (Kirton, Pharriss & Forbes, 1970). Since prostaglandins are very rapidly cleared by the pulmonary circulation, observed discrepancies may be due to the actual route of administration and dosage used.

Experiments have been carried out to measure the effect of PGF in producing parturition in the pregnant rabbit. PGF was infused continuously into rabbits with an indwelling aortic catheter (Nathanielsz & Abel, 1972). Infusions were started on day 21 and continued until delivery. PGF was infused at dose rates varying from 1·125 ng/h

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MARGARET H. ABEL, S. K. SMITH and D. T. BAIRD

Concentrations of prostaglandin F (PGF) and prostaglandin E (PGE) were measured in endometrium from 18 women with ectopic pregnancies. In the nine pregnancies not associated with vaginal bleeding or an intra-uterine contraceptive device (IUCD; intact ectopics), concentrations of PGF (12·8 ± 7·4 (s.e.m.) ng/g) and PGE (4·7 ± 3·0 ng/g) were similar to those in decidua from nine intra-uterine pregnancies of comparable gestational age (14·4 ± 4·4 and 8·2 ± 2·2 ng/g respectively). In both ectopic and intra-uterine pregnancies concentrations of prostaglandins were significantly lower than those found in endometrium throughout the normal menstrual cycle (P < 0·01). In nine ectopic pregnancies with associated vaginal bleeding and/or an IUCD, concentrations of PGF and PGE were significantly higher than in the intact group (P < 0·05), although the concentration of PGF remained significantly lower than levels in normal secretory endometrium (P < 0·05).

These results suggested that suppression of endometrial synthesis of prostaglandin during early pregnancy may be mediated systemically rather than through a local action of the conceptus.

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J. K. KULSKI, MARGARET SMITH and P. E. HARTMANN

Departments of Biochemistry and *Obstetrics and Gynaecology, University of Western Australia, Nedlands, Australia

(Received 25 April 1977)

The hormonal signal for lactogenesis in a number of different species is considered to be a precipitous fall in the concentration of progesterone in the blood during late pregnancy (see Hartmann, Trevethan & Shelton, 1973). In women, the major fall in the level of blood progesterone just after delivery (Yannone, McCurdy & Goldfien, 1968) precedes lactogenesis by 2-3 days (Reynolds, 1972). However, the effects of this fall may be modified to some extent by progesterone, which accumulates in the milk (Heap, Gwyn, Laing & Walters, 1973). Progesterone could be the 'lipid-soluble substance' in the mammary secretion which Linzell & Peaker (1974) suggested might control the final stage of lactogenesis. The purpose of the present investigation was to compare changes in the concentrations of progesterone, lactose and α-lactalbumin in the mammary secretion of women