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SUMMARY
The newly formed corpus luteum of many species is refractory to the lytic action of prostaglandin F2α (PGF2α). This phenomenon was studied utilizing porcine, bovine and human granulosa-luteal cells in tissue culture. The steroidogenic potential of the granulosa-luteal cells was critical in determining whether PGF2α could inhibit progesterone production. Since the steroidogenic potential of the granulosa-luteal cell is related to the amount of LH bound to the cell, the bound LH may protect the granulosa-luteal cells from the lytic action of PGF2α. Finally, a 'see-saw' type of interaction between LH and PGF2α is postulated to account for the resistance of the newly formed corpus luteum to PGF2α
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SUMMARY
Large and rapid variations were found in the plasma cortisol levels of housed and cannulated sheep. Adrenaline injected i.v. caused increased plasma levels of cortisol that were proportionate to the dose. This response of cortisol to adrenaline was larger when sheep were newly housed, than when the sheep had been housed and sampled for 2 weeks. Response to adrenocorticotrophin also diminished over 2 weeks. Dexamethasone abolished the response to adrenaline. Tyrosine and DOPA had little effect on cortisol levels, dopamine and noradrenaline had some effect, but none had as great an effect as adrenaline.
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The concentrations of FSH, oestradiol and androstenedione in the follicular fluid of normal and cystic human follicles were measured at different stages of the menstrual cycle. In addition, the number of granulosa cells in the follicles was determined.
In follicles in which FSH was detectable, the concentration of oestradiol was greater than that of androstenedione, irrespective of the stage of the cycle. In contrast, in those follicles in which FSH was undetectable and in all cystic follicles irrespective of the level of FSH, the concentration of androstenedione was greater than that of oestradiol. In follicles containing FSH there was a highly significant linear correlation between the number of granulosa cells and the concentration of follicular oestradiol (P < 0·001).
It is suggested that in human ovaries up to 90% of the oestradiol in follicular fluid may originate from the granulosa cells.
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SUMMARY
The steroidogenic potential of granulosa cells harvested from human Graafian follicles containing varying concentrations of pituitary and steroid hormones was examined. The mitotic activity and production of progesterone by granulosa cells in vitro was found to be correlated with their hormonal environment at the time of harvesting. Only cells from follicles containing some FSH and high concentrations of oestradiol underwent spontaneous mitosis in vitro. However, mitosis could be induced by adding FSH and high concentrations of oestradiol to the culture, provided that the concentration of LH was low. Cells harvested from follicles containing LH, FSH and high concentrations of oestradiol secreted significantly more progesterone than cells from follicles which did not contain all three hormones.
It is suggested that after the initiation of follicular development by FSH, a long period of exposure (8–10 days) to both FSH and oestradiol is necessary before the maximum biosynthetic capacity of granulosa cells is achieved; this synthetic potential is then only realized under the influence of LH and prolactin. Premature exposure to LH inhibits both the mitotic activity and the steroidogenic potential of these cells.
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Diurnal variation of cortisol in the peripheral plasma of sheep has been demonstrated after the animals had been allowed to adapt to the environment in which they were tested. This variation was not seen in sheep tested after only 7 days in their new environment (McNatty, Cashmore & Young, 1972). Although adapted sheep have higher plasma levels of cortisol in the morning daylight hours than during the remainder of the 24-h day (McNatty et al. 1972), it is not known whether this diurnal variation is re-established while sheep are habituating to their new environment. We have limited evidence to suggest that sheep require 14–28 days to become adapted to a new environment (D. C. Thurley & K. P. McNatty, unpublished observation).
We wish to describe the diurnal changes in the peripheral plasma cortisol levels of sheep while they are adapting to a new environment and exposed to diffuse light.
Nine
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Reports on diurnal variation in plasma corticosteroids in man, monkey, dog, rat, mouse and other species have been reviewed by Yates, Russell & Maran (1971) and by Yates & Urquhart (1962). We wish to report evidence of diurnal variation in the peripheral plasma cortisol levels of sheep, demonstrable after they had been allowed adequate time to adapt to the environment in which they were tested.
Three anoestrous New Zealand Romney ewes were placed indoors in crates with minimal restraints. They were placed immediately adjacent to each other and were free to sit or stand. They were given hay, lucerne pellets and water ad libitum. No attempt was made to regulate feeding and an excess of feed was ensured at all times. Each animal had an indwelling jugular cannula, inserted at least 3 h before the first sampling, which remained in situ throughout the experiment. On each occasion 10 ml blood
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SUMMARY
Human granulosa cells with differing steroidogenic potentials were cultured in vitro. The effects of prostaglandin F2α (PGF2α) and PGE2 on the progesterone output and viability of these cells were investigated.
Prostaglandin F2α either alone or in combination with LH and FSH inhibited the production of progesterone over a wide range of concentrations (1–8000 ng/ml). However, the inhibitory effect of PGF2α was 200 times less effective when the cells were exposed to LH and FSH for 6 days before the addition of the prostaglandin. By contrast PGE2, at concentrations from 1 to 500 ng/ml, markedly stimulated the production of progesterone by granulosa cells, and this was not prevented by the addition of PGF2α. The degree of inhibition by PGF2α or stimulation by PGE2 was related to the biosynthetic capacity of the cells.
These studies suggest that PGF2α may act directly on the adenylate cyclase system of human granulosa cells by blocking its activation by LH, and they demonstrate that functional regression of the luteal cell can be induced independently of the blood vascular system.
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Search for other papers by K. J. A. REVFEIM in
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SUMMARY
Progesterone concentrations in peripheral plasma were measured once daily during one oestrous cycle in each of eight sheep. In addition, on days 4–5, 8–9, 12–13 and 15–16 of the oestrous cycle, blood samples were collected at 30-min intervals throughout each 24-h period. A total of three ewes was sampled in each 24-h period and the same three animals were not bled again for at least 1 week. Plasma progesterone concentrations in all the ewes fluctuated considerably throughout each 24-h period. The within-sheep within-day variations observed in peripheral progesterone concentrations were compared with the between-sheep within-day variations and the within-sheep between-day variations previously reported. It is concluded that these previously reported variations in peripheral plasma progesterone concentration could be attributed to within-day variations in each animal.
On days 8–9 and 12–13 of the oestrous cycle there were significantly higher concentrations of progesterone in plasma during the hours of daylight than during the hours of darkness. In contrast, progesterone concentrations on days 4–5 and 15–16 were not found to be significantly different between the hours of daylight and darkness. These results suggest that diurnal changes in peripheral plasma progesterone concentration occur during the luteal phase of the ovine oestrous cycle.
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Search for other papers by K P McNatty in
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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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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
