The Effects of Ici 33828 and Progesterone on Oestrogen-Maintained Corpora Lutea in the Sow

Garbers, David L.; First, N. L.

doi:10.1530/jrf.0.0190541

Cited by 3 publications

(1 citation statement)

References 11 publications

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“…Mitchell (1966Mitchell ( , 1967 showed that avian gonadotrophins could stimulate the bird ovary in the presence of ICI 33828 treatment. Garbers & First (1969b) have shown that ICI 33828 does not reduce cl weight in oestrogen-treated gilts, indicating that the drug appears to act at some site other than the gonads. Brown (1963) presented pituitary information suggesting that the compound acted at the pituitary or hypothalamic levels.…”

Section: Discussionmentioning

confidence: 99%

The Effects of Injected Oestradiol-17 , Progesterone and Dietary Ici 33828 on Ovarian and Pituitary Functions in the Sow and Gilt

Dl¹,

Nl²

1969

Reproduction

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Two experiments using twenty-four sows and forty-eight gilts were designed to study ovarian and pituitary functions after treatment with oestradiol-17\g=b\(3 mg/day), progesterone (150 mg/day) or ICI 33828 (50 or 100 mg/day). The dose levels were chosen so that oestrus and ovulation would be inhibited.None of the treatments blocked total synthesis of fsh or lh within the 10-day treatment period. ICI 33828 at 100 mg blocked fsh release early in the cycle but 50 mg did not. Oestrogen also blocked fsh release early in the cycle. All follicle growth greater than 4 mm diameter was effectively inhibited by oestrogen and the corpora lutea were maintained. Both progesterone and ICI 33828 reduced the number of follicles growing larger than 5 mm as compared to the control gilts. All treatments blocked fsh release late in the cycle.There were increased levels of pituitary lh in ICI 33828-treated gilts compared to progesterone-treated gilts early in the cycle, but none of the treatments caused differences in lh levels from those found in the control gilts early in the cycle. All treatments blocked pituitary lh release late in the oestrous cycle.The pituitary content of prolactin did not differ significantly between treatments.

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Section: Discussionmentioning

confidence: 99%

The Effects of Injected Oestradiol-17 , Progesterone and Dietary Ici 33828 on Ovarian and Pituitary Functions in the Sow and Gilt

Dl¹,

Nl²

1969

Reproduction

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Estrous synchronization and fertility in gilts treated with estradiol-benzoate and prostaglandin F2α

Guthrie

1975

Theriogenology

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Bipotential Actions of Estrogen on Progesterone Biosynthesis by Ovarian Cells. I. Relation of Estradiol's Inhibitory Actions to Cholesterol and Progestin Metabolism in Cultured Swine Granulosa Cells*

et al. 1985

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In short term, serum-free cultures of granulosa cells, estradiol inhibited basal progesterone production by more than 84% in a time- and dose-dependent fashion. Half-maximal inhibition (ID50) was observed at a mean estradiol concentration of 70 ng/ml. The acute inhibitory effects of estradiol were independent of cell density or maturational status of the parent follicle (small, medium, or large follicles). Estrogen decreased total progesterone biosynthesis, rather than merely progesterone secretion by granulosa cells. In addition, the production of progesterone and its 20 alpha-reduced metabolite were suppressed in parallel over a 30-fold range of inhibitory effects. Moreover, estradiol inhibited progesterone production from both endogenous and exogenous (25-hydroxycholesterol) substrate. In contrast to its inhibition of progesterone production, estradiol acutely enhanced pregnenolone accumulation and led to a 14- to 20-fold increase in the ratio of pregnenolone to progesterone. Inhibition of 3 beta-hydroxysteroid dehydrogenase activity was confirmed by demonstrating estrogen's ability to antagonize the conversion of exogenously supplied pregnenolone to progesterone in intact granulosa cells (ID50, 74 ng/ml) and to directly inhibit enzymic activity in ovarian homogenates (ID50, 79 ng/ml). On the other hand, estradiol did not alter the incorporation of [14C]acetate into cholesterol and specific progestins or influence the time-dependent hydrolysis of prelabeled cholesteryl ester stores in granulosa cells. In summary, in short term cultures of swine granulosa cells, estradiol significantly inhibits basal progesterone biosynthesis in a time- and dose-dependent fashion, encompassing estradiol concentrations attainable in vivo. Estrogen's inhibition is accomplished by mechanisms that are independent of cytotoxicity, cell density, and maturational stage of the parent follicle. The predominant locus of estrogen action is blockade of pregnenolone's conversion to progesterone, rather than accelerated metabolism of progesterone to its 20 alpha-reduced metabolite. Moreover, estradiol simultaneously enhances functional cholesterol side-chain cleavage activity without suppressing de novo cholesterol biosynthesis or impairing the mobilization of cellular cholesteryl ester stores. Thus, we infer that increasing concentrations of estradiol attained in antral follicular fluid during the later stages of follicle maturation could effectively limit the premature secretion of large quantities of progesterone before ovulation without impairing the cell's capacity for de novo cholesterol biosynthesis or cholesteryl ester hydrolysis.

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The Effects of Ici 33828 and Progesterone on Oestrogen-Maintained Corpora Lutea in the Sow

Cited by 3 publications

References 11 publications

The Effects of Injected Oestradiol-17 , Progesterone and Dietary Ici 33828 on Ovarian and Pituitary Functions in the Sow and Gilt

The Effects of Injected Oestradiol-17 , Progesterone and Dietary Ici 33828 on Ovarian and Pituitary Functions in the Sow and Gilt

Estrous synchronization and fertility in gilts treated with estradiol-benzoate and prostaglandin F2α

Bipotential Actions of Estrogen on Progesterone Biosynthesis by Ovarian Cells. I. Relation of Estradiol's Inhibitory Actions to Cholesterol and Progestin Metabolism in Cultured Swine Granulosa Cells*

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