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I. A. SWANSTON, K. P. McNATTY and D. T. BAIRD

SUMMARY

The concentration of prostaglandin F (PGF), progesterone, pregnenolone, oestradiol-17β, oestrone, androstenedione and testosterone was measured in corpora lutea obtained from 40 women at various stages of the menstrual cycle. The concentration of PGF was significantly higher in corpora lutea immediately after ovulation (26·7 ± 3·9 (s.e.m.) ng/g, P < 0·005) and in corpora albicantia (16·3 ± 3·3 ng/g, P < 0·005) than at any other time during the luteal phase. There was no correlation between the concentration of PGF and that of any steroid. The progesterone concentration was highest in corpora lutea just after ovulation (24·9 ± 6·7 μg/g) and in early luteal groups (25·7 ± 6·8 μg/g) but declined significantly (P < 0·05) to its lowest level in corpora albicantia (1·82 ± 0·66 μg/g). The concentration of oestradiol-17β in the corpus luteum and luteal weight were significantly greater during the mid-luteal phase than at any other stage (concentration 282 ± 43 ng/g, P < 0·05; weight 1·86 ± 0·18 g, P < 0·005).

The results indicate that regression of the human corpus luteum is not caused by a rise in the ovarian concentration of PGF in the late luteal phase of the cycle.

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L. Westergaard, K. P. McNatty and I. J. Christensen

ABSTRACT

Steroid concentrations in fluid from 138 ovarian antral follicles obtained from 30 pregnant women were measured and compared with those in aspirates of 151 follicles of similar size (i.e. diameter 2–6 mm) from 61 non-pregnant women who had normal regular menstruations. The follicles were classified as healthy or atretic by flow cytometric DNA measurement of the granulosa cells contained in the follicular fluid aspirate.

Nine (7%) of the follicles from pregnant women and 21 (14%) of those from non-pregnant women were healthy, and the remainder atretic (P>0·05). Androstenedione was the most abundant steroid in all follicles. Mean progesterone levels in follicular fluid from pregnant women were significantly (P<0·05) higher than in follicular fluid from non-pregnant women. In pregnant women progesterone levels were significantly (P<0·01) higher in fluid from healthy than from atretic follicles. In contrast, no significant differences in steroid concentrations were found between fluid from healthy and atretic follicles in non-pregnant women.

We conclude that antral ovarian follicles may develop normally to a diameter of around 6 mm during the third trimester of human pregnancy. We also conclude that these follicles accumulate steroids in the follicular fluid in amounts which equal those found in follicles of similar size in the ovaries of non-pregnant women, but that the composition of intrafollicular steroids during pregnancy is modified towards higher concentration of progesterone. The reason for this increased intrafollicular progesterone level is unclear.

J. Endocr. (1985) 107, 133–136

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K. P. McNATTY, MARION GIBB, CAROLYN DOBSON and D. C. THURLEY

The aim of the present study was to gain evidence that the level of LH secretion preceding the preovulatory LH surge is an important determinant of follicular maturation and corpus luteum function in the ewe. In addition it was hoped to establish whether the pattern of LH delivery to the ovary (pulsatile v. constant) is a critical factor in the maturation of a preovulatory follicle.

To accomplish this, progesterone-primed anoestrous ewes were repeatedly injected i.v. with LH or luteinizing hormone-releasing hormone (LH-RH), or given an i.v. infusion of LH, over a 72 h period. These animals, together with the appropriate controls, were exposed to a sexually active ram so that oestrous activity could be recorded. All ewes were subjected to intensive blood sampling regimes so that the plasma levels of LH and progesterone could be determined and compared to those which occurred in the same breed of sheep during the oestrous cycle.

Collectively the data suggest that the plasma levels of LH preceding the preovulatory LH surge are an important determinant of follicular maturation as judged by subsequent corpus luteum function. Moreover, they show that follicular maturation can be achieved with widely differing patterns of LH delivery to the ovary during the preovulatory period and that a strict pulsatile delivery of LH may not be an absolute requirement.

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D J Phillips, K P McNatty, P Smith, K Pettersson and L Wide

Abstract

The heterogeneity of LH and FSH in the sheep fetus was studied by determining the median charge of pituitary and circulating isoforms. Pituitary extracts from male and female fetuses at days 75, 95, 120 and 135 of gestation were subjected to agarose suspension electrophoresis. For all fetuses except the day 75 age group, the median mobility of the gonadotrophin isoforms in matching serum samples from the individual fetuses were also determined. LH and FSH in extracts, peripheral samples and column eluates were measured using sensitive and specific sandwich fluoroimmunoassays for ovine gonadotrophins. The median charge of pituitary LH became more basic (P<0·001) with gestational age, whereas for pituitary FSH more acidic forms (P<0·001) were present in the older groups. The female fetuses had more basic pituitary isoforms of LH than the males (P<0·01) between days 95 and 135, and for FSH at day 75 (P<0·05). In the matching serum samples, the median charge of the LH (P<0·001) and FSH (P<0·05) isoforms were more acidic than those in the pituitary gland. No significant effects of age or sex were detected in the median charge of the gonadotrophin isoforms in serum, but in a number of instances the median charge could not be determined due to low serum concentrations which affected the group sizes. These data show that in the sheep fetus LH and FSH are differentially regulated in qualitative as well as quantitative terms, and that the charge of fetal gonadotrophin isoforms changes according to the age and sex of the fetus.

Journal of Endocrinology (1996) 149, 29–39

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L G Moore, K P McNatty, K L Isaacs, S Lun, W Ng Chie, S McNatty and N L Hudson

Abstract

The aim of this study was to examine the effect of the FecBB fecundity gene on plasma concentrations and pituitary content of growth hormone (GH) in sheep. No differences were found between homozygous carriers (BB) and non carriers (++) of the FecBB gene with regard to pituitary GH contents in both ovariectomized and intact ewes. However, ovariectomized ewes had higher levels of pituitary GH than intact ewes (P<0·01). There were no differences between FecBB genotypes with respect to plasma concentrations of GH in 6-year-old ovariectomized ewes bled every 10 min for 12 h or in ram lambs bled weekly during their first year of life. GH levels in the rams decreased until week 27, increased to a peak at week 31 then decreased before increasing again at week 43. Mean plasma GH concentrations in the ewe lambs bled weekly for a year decreased until week 19 then remained at approximately this level for the remainder of the year. Mean GH plasma concentrations in the ram lambs were higher than in the ewe lambs (P<0·001). Ewe lambs that were homozygous for the FecBB gene had lower body weights (P<0·05) and had higher levels of GH (P<0·01) than non carrier ewe lambs during their first year. Before the average age of first behavioural oestrus (36 weeks) GH levels in the ewe lambs were negatively correlated with body weights (r=−0·69, P<0·001, n=22). When body weight was included as a covariate in analysis of variance the genotype difference in ewe lamb plasma GH concentrations was no longer significant. In summary, pituitaries from ovariectomized ewes had higher levels of GH than those from intact ewes. There were no FecBB gene specific differences in pituitary levels of GH, the profile of plasma GH in 6-year-old ovariectomized ewes or in ram lambs during their first year of life. BB ewe lambs had higher levels of GH than ++ ewe lambs during their first year; however, this difference was probably due to the BB ewes having lower body weights than the ++ ewes because body weight was negatively correlated with mean GH levels.

Journal of Endocrinology (1995) 147, 217–223

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K. P. McNatty, N. Hudson, M. Gibb, K. Ball, J. Fannin, L. Kieboom and D. C. Thurley

ABSTRACT

The aim of the present study was to establish whether cyclic ovarian activity could be induced and then maintained in anoestrous Romney ewes by the long-term administration of regular intravenous pulses of LH (10 μg ovine LH i.v. once every 1 or 2 h for 29–91 days). The LH pulse regimen was designed to generate plasma profiles of LH that were comparable to those experienced during the luteal and follicular phases of the oestrous cycle.

The results showed that the LH treatments were capable of inducing cyclic ovarian activity, as assessed from the concentrations of progesterone in plasma, but that the treatments were inadequate for sustaining cyclic activity beyond two consecutive progestational phases. After 35–56 days of treatment, the plasma concentrations of FSH declined significantly (P <0·05) relative to those in the untreated animals. These data suggest that FSH supplementation as well as LH might be required for the long-term maintenance of cyclic ovarian activity in seasonally anoestrous ewes.

J. Endocr. (1984) 100, 67–73

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D. J. Phillips, P. R. Smith, D. A. Heath, L. A. Condell and K. P. McNatty

ABSTRACT

The bioactive (B) and immunoreactive (I) pituitary contents/concentrations of FSH, together with the plasma concentrations of B-FSH, I-FSH and I-inhibin were determined in ovine fetuses at days 55, 75, 90 and 135 of gestation (day 145 = term). The pituitary contents and concentrations of B-FSH and I-FSH increased in both sexes with gestational age. The female fetuses had significantly (P <0·01) higher pituitary contents/concentrations of B-FSH and I-FSH than the male fetuses at days 75 and 135. The pituitary B/I ratios of FSH were not significantly different with age or sex. The plasma concentrations of B-FSH remained relatively constant from days 75 to 135, with no significant differences between sexes or with age. In contrast, the plasma concentrations of I-FSH reached a peak at day 90 and then declined towards term in both sexes. At all gestational ages except day 55, the female fetuses had significantly (P <0·05) higher plasma concentrations of I-FSH than the males. In both sexes, the plasma B/I ratios of FSH were lowest at day 90 and had increased again by day 135, with the male fetuses having significantly (P <0·05) higher B/I ratios compared with the female group at days 75 and 135 but not at day 90. At all gestational ages, the plasma concentrations of I-inhibin declined throughout gestation in the female fetuses, whereas in the males they reached a nadir at day 75 and then increased towards term. The concentrations of I-inhibin were significantly (P <0·01) higher in the male fetuses compared with the females. Collectively, these data suggest that there are changes in the forms of FSH present in the pituitary gland and plasma throughout gestation in the ovine fetus. Moreover, they infer that the difference between the sexes in FSH synthesis and/or secretion may be attributed in part to the circulating concentrations of inhibin.

Journal of Endocrinology (1992) 134, 287–295

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B R Leeuwenberg, N L Hudson, L G Moore, P R Hurst and K P McNatty

Abstract

IGF-I was measured by RIA in plasma samples collected 8-hourly for 24 days which included two consecutive preovulatory surges of LH. In a separate study, ovarian venous blood was collected from animals undergoing ovariectomy on day 10 of the oestrous cycle, or 36 h later after being treated with prostaglandin with or without steroid-free bovine follicular fluid. Jugular venous blood samples were collected before, during and after surgery. Follicles were dissected from ovaries of these animals and sorted into categories of small, intermediate and large, non-atretic or atretic, and the follicular fluid was pooled and assayed for IGF-I. From another population of ovaries recovered from the slaughterhouse, granulosa, theca and corpora lutea were isolated, homogenized and assayed for IGF-I. Finally ovarian corpora lutea and granulosa cells were each incubated with tritiated amino acids overnight at 37 °C. Thereafter the tissues and media were sonicated, IGF-I extracted from the supernatant and tritiated IGF-I precipitated using a specific IGF-I antibody.

The absence of any significant change in peripheral IGF-I concentrations following ovariectomy and the finding that the ovarian venous IGF-I concentrations (161 ± 10 μg/l) were not significantly different from levels seen in peripheral blood (157 ± 10 μg/l) indicated that the ovary is not a net exporter of IGF-I. However, the ovary does synthesize IGF-I, as evidenced by granulosa and luteal synthesis, but probably not in quantities in excess of that utilized by ovarian tissues per se. Although the plasma IGF-I levels increased around the second preovulatory LH surge, the results overall indicated that the IGF-I concentrations in plasma are not strictly related to any major ovarian event during the oestrous cycle in the sheep. This view is based on the findings that the concentration of IGF-I in follicular fluid was not related to follicular health but correlated with those in peripheral plasma and that the ovarian venous concentrations did not vary between left and right ovaries irrespective of whether the ovaries contained a corpus luteum, dominant follicle or neither. Collectively, these results are consistent with the notion that IGF-I of ovarian origin fulfils an autocrine/paracrine function and does not have an endocrine role. Moreover, the results show that the concentrations of IGF-I in follicular fluid reflect those in peripheral plasma.

Journal of Endocrinology (1996) 148, 281–289

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P. NEAL, T. G. BAKER, K. P. McNATTY and R. J. SCARAMUZZI

SUMMARY

The response of mouse ovaries maintained in organ culture to prostaglandin E2 (PGE2) and prostaglandin F (F2α) was assessed using quantitative histological and radioimmunoassay procedures.

Prostaglandin E2 induced histological changes in the cultured follicles comparable to those induced by human chorionic gonadotrophin (HCG) and the increase in the number of oocytes undergoing preovulatory maturation over the control value was the same irrespective of the treatment (PGE2 alone, HCG alone, or PGE2 + HCG). The amount of progesterone/ ml of culture medium was also significantly higher with these preparations than in control cultures (about 125 ng/ml compared with 57 ng/ml).

By contrast, 5 μg PGF2α/ml medium increased neither the number of oocytes undergoing maturation nor the concentration of progesterone in the culture medium. The latter increased when the dose of PGF2α was increased to 30 μg/ml, although the proportion of oocytes beyond the dictyate stage remained at the control level. There was no augmentation in the response (above the level for HCG alone) when HCG and PGF2α were added to the explant medium simultaneously. These results are discussed in terms of the possible mechanism of action of the various preparations.

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K. P. McNATTY, D. T. BAIRD, A. BOLTON, P. CHAMBERS, C. S. CORKER and H. McLEAN

SUMMARY

The concentrations of androstenedione, testosterone, oestrone and oestradiol-17β were measured in peripheral and ovarian venous blood and follicular fluid of women at various stages of the menstrual cycle. The concentration of oestradiol was similar in small follicles (diameter < 8 mm) at all stages of the menstrual cycle and in large follicles (diameter ⩾ 8 mm) except during the mid- and late follicular phase when the concentration reached a peak (∼ 1500 ng/ml).

The concentration of androstenedione was lowest in large preovulatory follicles at mid-cycle at a time when the secretion into the ovarian vein was markedly increased. The concentration of testosterone in large follicles (⩾ 8 mm) was unchanged during the follicular phase whereas in small follicles there was a peak at mid-cycle.

The rise in the concentration of testosterone and androstenedione at mid-cycle in peripheral plasma may be due to increased secretion by the preovulatory follicle into the ovarian vein. It is suggested that the relatively low concentration of androstenedione in follicular fluid of the preovulatory follicle arises from increased aromatization by granulosa cells in the course of oestrogen synthesis.