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Using the intravaginal tetrazolium method of Martin (1964), the oestrogenic activity in plasma samples (5–10ml.) taken monthly from three sows during pregnancy has been estimated.

(1) 'Free' oestrogens were extracted from the plasma with ethyl acetate. This extract was passed through a florisil column to remove corticosteroids and oestriol (Saba, 1964a). The eluate, which would contain oestradiol, oestrone and progesterone, was evaporated to dryness. The dry residue was taken up in a mixture of benzene—petroleum ether (50:50, v/v) and the phenolic oestrogens were extracted with n-NaOH. This alkaline extract was acidified and extracted with ether (Saba, 1964b).

(2) 'Bound' oestrogen. After removal of the residual ethyl acetate, the plasma was hydrolysed in 1·5n-HCI (Preedy & Aitken, 1957) and extracted with ether as described above. The residue was partitioned between benzene—petroleum ether and NaOH as under (1).

The mean recovery of oestrone added to plasma

Little is known of the changes occurring in the liver during pregnancy and lactation. The ratios of liver weight and liver protein to body weight are increased in pregnant rats [Bokelmann & Scheringer, 1932], and more of the maternal protein is apportioned to the liver in pregnant rats than in non-pregnant controls [Poo, Lew & Addis, 1939; Poo, Lew, Lee & Addis, 1940]. The total nucleic acid content is considerably raised, both deoxyribonucleic and ribonucleic acids taking part [Davidson & Waymouth, 1944]. There is an increase of the ascorbic acid content of the livers of mice and rats during pregnancy [Kennaway & Kennaway, 1944; Kennaway & Tipler, 1947]. The arginase content of the liver of rats is normal during pregnancy but increased during lactation [Folley & Greenbaum, 1947].

Since during pregnancy and lactation the maternal organism has to provide the material for a very rapid protein synthesis, considerable changes in

SUMMARY

The concentration of testosterone was measured in the plasma of 16 healthy women in late pregnancy and in 14 of these after delivery. The mean testosterone concentration was found to be elevated in late pregnancy, although the range overlapped with the normal. There was a prompt return to normal concentrations after delivery. The significance of the results and of inactivation of testosterone by protein binding are discussed.

Abstract

In this study we report the immunolocalization, binding and biological activity of endothelins in the human uterus. Since, in previous studies in the rabbit, sex steroids greatly affected uterine endothelin-1 (ET-1) immunolocalization and binding, we sought to compare results obtained in a relatively steroid-deprived uterus (postmenopausal women) with those obtained in late pregnancy. Two classes of ET receptors were identified in human pregnant and non-pregnant myometrium. One site (ET_B) was a low capacity site (0·3 pm/mg protein) that bound with high affinity (0·1 nm), yet no selectivity, ET-1, ET-2, ET-3, sarafotoxin (SRTX) and vasoactive intestinal contractor (VIC). The second site (ET_A) was six fold more concentrated than the former (1·9 pm/mg protein) and was relatively selective for ET-1, ET-2 and VIC but showed lower affinity for ET-3 and SRTX. Studies with human myometrial cells indicated that the ET_A receptor mediates an increase in intracellular calcium, while the physiological function of the ET_B receptor is still unclear. Homologous competition curves for ET-1 were used in order to study the ET receptor density (ET_A+ET_B) in individual myometrial samples. We found that the concentration of ET receptors did not change during different stages of labour or in postmenopausal women. We identified cells with intense positivity for ET-1 in human decidua. Similar cells were also present in pregnant myometrium, intimately associated with smooth muscle cells. Conversely, no staining for ET-1 was observed in non-pregnant myometrium. A paracrine role for ET-1 in the human uterus is suggested.

Journal of Endocrinology (1994) 142, 385–396

Abstract

Activin A (β_A–β_A) and activin B (β_B–β_B) are related dimeric proteins that regulate numerous cellular activities. Activin activity is bioneutralized by follistatin, a specific and high-affinity binding protein. Recently, our group developed specific and sensitive enzyme-linked immunosorbent activin assays that do not detect either activin isoform when bound to follistatin, therefore, the assays are specific for biologically relevant ligands. Activin A is measurable in the serum of pregnant women (cross-sectional sample collection), while activin B is not detected in maternal serum. However, activin B is measurable in amniotic fluid and cord blood sera. The purpose of this study was to measure serum activin A, activin B, and follistatin prospectively in longitudinally collected samples during pregnancy. This study design offered observations of relative changes in serum hormone concentration with each person serving as an internal reference.

Serum samples were collected bimonthly from seven pregnant women beginning within the second month of gestation, and up to, but not including, the onset of labor. Six of the seven women had normal labor and delivery. One patient required pitocin (an oxytocin agonist) for induction of labor which led to delivery. Activin A, activin B, total follistatin, free follistatin, human chorionic gonadotropin, estradiol, progesterone, FSH, and LH were measured in maternal serum samples using specific assays.

Serum activin A levels increased in the final month of pregnancy in the six patients who delivered following normal labor (<0·78 ng/ml (first trimester) to 1–6 ng/ml (term)). Activin B was not detected in any serum sample (<0·78 pg/ml). Total serum follistatin (free follistatin, follistatin–activin, and follistatin–inhibin) increased 10- to 45-fold in the final month of pregnancy in four of the women undergoing normal labor (10 ng/ml (first trimester) to 100–450 ng/ml (final month)). Total follistatin was high and variable in two women throughout pregnancy. Total follistatin returned to basal serum concentration in three of the patients during the last 2 weeks of pregnancy. Free follistatin was detected throughout pregnancy (range <2–35 ng/ml). Free follistatin represented a small percentage of the total follistatin throughout the time of pregnancy and did not rise coincident with the rise in total follistatin. Serum activin A and activin B were not detected during the entire course of pregnancy in the one patient who did not have normal labor and total follistatin did not rise in the last trimester of pregnancy. Gonadotropin and steroid hormones were measured in all patients and were within normative ranges for human pregnancy (inclusive of the non-laboring patient).

The results suggest that immunodetectable activin A is present in the third trimester of pregnant women who have normal onset labor. The total follistatin assay results suggest that follistatin–activin (or –inhibin) complexes are upregulated during the third trimester of pregnancy. Importantly, activin A production exceeds the binding capacity of circulating follistatin. Because binding protein free activin A is biologically active we conclude that the activin A detected in late pregnancy is biologically relevant. The findings are consistent with our hypothesis that activin A is an endocrine factor during the last trimester of human pregnancy and may be involved in normal labor.

Journal of Endocrinology (1997) 152, 167–174

Testosterone concentrations in serum of rats bled throughout pregnancy and post partum were measured using Celite microcolumn chromatography and a radioimmunoassay for testosterone. Mean serum levels of testosterone ranged from about 170 to 340 pmol/l during the first 10 days of pregnancy. Significant increases in concentrations of testosterone in serum of pregnant rats were found on days 12, 15 and 18 of gestation. The highest testosterone concentrations occurred on days 18 and 20 of pregnancy when mean levels were 3228 and 3685 pmol/l respectively. Testosterone levels declined before parturition on day 22 (mean = 1449 pmol/l and declined further after parturition (mean = 315 pmol/l). In order to determine whether serum testosterone concentrations varied during the day in the pregnant rat, samples were collected at 6-h intervals on days 6–7 and 14–15 of gestation. Diurnal variations in serum testosterone concentrations were not evident during early or late pregnancy, unlike the rhythmic changes in serum prolactin levels found at these times during early pregnancy. The possible sources of the increased titres of serum testosterone during the second part of gestation in rats are discussed.