Steroid concentrations in rat corpora lutea isolated during the oestrous cycle and pseudopregnancy: effect of induction of ovulation at dioestrus

Uilenbroek, J. Th. J.; Woutersen, P. J. A.; Vaart, P. D. M. van der

doi:10.1677/joe.0.1200325

Cited by 5 publications

(4 citation statements)

References 13 publications

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“…Hormone measurements. The amounts of progesterone and (20u-hydroxypregn-4-ene-3-one 20u-dihydroprogesterone) in blood and corpus luteum homogenates were measured by radioimmunoassay following the procedure described by Uilenbroek et al (1989). The intra-and inter-assay variations were 8% and 20% respectively.…”

Section: Methodsmentioning

confidence: 99%

Failure of two progesterone antagonists, mifepristone and onapristone, to affect luteal activity in lactating rats

Schoot

Uilenbroek²,

Slappendel³

1989

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The progesterone antagonists, mifepristone (RU-38,486) and onapristone (ZK-98,299), given as 2 mg daily, did not markedly affect lactation in rats. Both litter growth and time spent by 10-pup litters attached to their mothers were similar in antagonist-treated mothers and in solvent-treated controls. The progesterone antagonists did not affect the steroid content in corpora lutea remaining from the preceding pregnancy. Corpora lutea formed after post-partum ovulation also showed nearly normal function throughout the first 17 days of lactation. It is concluded that progesterone itself plays no role in the initiation or maintenance of luteal function when prolactin secretion is governed through an action independent of the ovaries, as through suckling. Antagonist-treated rats ovulated around Day 13 of lactation despite suckling. This ovulation was not associated with a decrease of progesterone production by the corpora lutea formed after post-partum ovulation. Apparently, elimination of progesterone action may protect corpora lutea from luteolysis. The latter finding indicates a possible role of progesterone in luteolysis and deserves further analysis.

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Section: Methodsmentioning

confidence: 99%

Failure of two progesterone antagonists, mifepristone and onapristone, to affect luteal activity in lactating rats

Schoot

Uilenbroek²,

Slappendel³

1989

Reproduction

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“…Half of the rats in each group were killed at 10.00 h on the morning of pro-oestrus (day 4). Seven corpora lutea of the last generation were dissected from each rat and weighed as previously described (Uilenbroek, Woutersen & van der Vaart, 1989). Four of these corpora lutea were homogenized individually in 1 ml absolute ethanol and stored at -20°C to determine the progesterone content.…”

Section: Methodsmentioning

confidence: 99%

“…The combined supernatants were evaporated to dryness and redissolved in 1 ml phosphate-buffered saline (001 mol/1, pH 7-0) containing 015% (w/v) gelatin. Thereafter, the progesterone concentrations were measured by RIA as described previously (Uilenbroek et al 1989). The progesterone antibody was a gift from Dr F. H. de Jong (Department of Endocrinology and Reproduction, Erasmus Univer¬ sity, Rotterdam, The Netherlands) and showed less than 001% cross-reaction with RU486.…”

Section: Methodsmentioning

confidence: 99%

Different effects of the antiprogesterone RU486 on progesterone secretion by the corpus luteum of rats with 4- and 5-day oestrous cycles

Sánchez-Criado

Uilenbroek²,

Karels³

1992

Journal of Endocrinology

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Administration of the antiprogesterone RU486 (2 mg/day) for 14 days to rats with a 5-day reproductive cycle resulted in an increase in both ovarian and pituitary weight in contrast with rats with a 4-day oestrous cycle. Luteal progesterone production decreased earlier in 4-day than in 5-day cyclic rats. Treatment of 5-day cyclic rats with antiprogesterone from the day of metoestrus onwards resulted in the advancement of the preovulatory prolactin surge by 24 h. Progesterone production by the corpus luteum was, however, not affected, indicating that in 5-day cyclic rats the corpora lutea are still functionally active at the time of the preovulatory surge of prolactin. They become, therefore, stimulated both in size and progesterone production. In contrast, the corpora lutea in 4-day cyclic rats are functionally inactive at the time of the preovulatory surge of prolactin, and prolactin acts luteolytically. In conclusion, the advancement of the preovulatory surge of prolactin by 24 h accounts, at least in part, for the increase in ovarian weight in 5-day cyclic rats after treatment with antiprogesterone. The results of these experiments do not agree with a direct effect of the antiprogesterone RU486 on progesterone secretion by the corpus luteum.

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“…In some experiments, 20 m SU-10603 was also added to inhibit residual activities of 17␣-hydroxylase/desmolase. Steroids in culture medium (300 l) or sonified cells (see below) were measured with RIAs previously described for pregnenolone (10,11), 20␣-dihydroprogesterone (13), and progesterone (14). The steroid specificities of the three antisera used are given in Table 1.…”

Section: Rpmimentioning

confidence: 99%

Implications of Progesterone Metabolism in MA-10 Cells for Accurate Measurement of the Rate of Steroidogenesis

Rommerts¹

2001

Endocrinology

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In virtually all studies with MA-10 cells, progesterone RIAs have been used to measure steroid synthesis. To test whether progesterone is a stable end product, we investigated the metabolism of added tritiated progesterone and pregnenolone in MA-10 cells over a period of 3 h. Steroids were then extracted, separated by HPLC, and identified by GC/MS. We found that more than 70% of radiolabeled steroids were converted to at least five different metabolites. A major metabolite (40%) was 5 alpha-pregnan-3 alpha or 3 beta-ol-20one. Similar studies, using radiolabeled T, demonstrated conversion to dihydrotestosterone and two forms of 5 alpha-androstane-diols. These data indicate the presence of active 5 alpha-reductase and 3 alpha- and/or 3 beta-hydroxysteroid dehydrogenase activities in MA-10 cells. Because these results suggest that progesterone is an unstable end product, to gauge the level of active metabolism, we incubated cells in the presence of inhibitors of pregnenolone metabolism and assessed pregnenolone levels by RIA. We discovered that basal levels of steroidogenesis in MA-10 cells were considerably higher than previously estimated. Moreover, dibutyryl cAMP-stimulated steroid production was linear over more than 13 h, in contrast to previous findings that measured progesterone levels. Other consequences of inaccurate assessment of steroidogenic activity in MA-10 cells because of the application of the progesterone assay are discussed.

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Steroid concentrations in rat corpora lutea isolated during the oestrous cycle and pseudopregnancy: effect of induction of ovulation at dioestrus

Cited by 5 publications

References 13 publications

Failure of two progesterone antagonists, mifepristone and onapristone, to affect luteal activity in lactating rats

Failure of two progesterone antagonists, mifepristone and onapristone, to affect luteal activity in lactating rats

Different effects of the antiprogesterone RU486 on progesterone secretion by the corpus luteum of rats with 4- and 5-day oestrous cycles

Implications of Progesterone Metabolism in MA-10 Cells for Accurate Measurement of the Rate of Steroidogenesis

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