Regulation of 3 beta-hydroxysteroid dehydrogenase delta 5/delta 4-isomerase and cholesterol side-chain cleavage cytochrome P450 by activin in rat granulosa cells.

The earliest biochemical indicators of ovarian follicle deviation in cattle include lower oestradiol and free IGF concentrations in subordinate compared with dominant follicles. We determined if decreases in FSH, IGF-I or insulin cause decreased P450 aromatase (P450arom) or P450 cholesterol side-chain cleavage (P450scc) mRNA expression in oestrogenic bovine granulosa cells in vitro. In the first experiment, cells obtained from small follicles (2-5 mm diameter) were cultured in serum-free medium supplemented with physiological concentrations of FSH, IGF-I and insulin for 4 days. A decrease in specific hormone concentration was produced by replacing 70% of spent medium with medium devoid of FSH, insulin, or insulin and IGF-I on day 4 and again on day 5 of culture. Cultures were terminated on day 7. A reduction in FSH concentrations during the last 3 days of culture decreased P450arom and P450scc mRNA levels. A reduction in insulin reduced P450arom but not P450scc mRNA levels, and a reduction of both insulin and IGF-I concentrations further decreased P450arom mRNA levels and decreased P450scc mRNA levels. In a second experiment, cells obtained from small follicles (2-5 mm diameter) were cultured with insulin (100 ng/ml) without FSH for 4 days, and then insulin was withdrawn from the culture and FSH added for a further 3 days. The withdrawal of insulin decreased (P<0.02) oestradiol accumulation and reduced P450arom mRNA to below detectable levels, but did not affect P450scc mRNA levels. The addition of FSH transiently increased oestradiol secretion and P450arom mRNA levels, but P450arom mRNA levels were undetectable at the end of the culture period. The addition of FSH significantly enhanced P450scc mRNA levels and progesterone accumulation. These data demonstrated that a reduction of insulin-like activity reduced aromatase gene expression in bovine follicles without necessarily affecting progesterone synthetic capability, and thus may initiate follicle regression in cattle at the time of follicle divergence.

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Regulation of cytochrome P450 cholesterol side-chain cleavage, 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase type 1 and estradiol-17β-hydroxysteroid dehydrogenase mRNA levels by calcium in human choriocarcinoma JEG-3 cells

Molecular and Cellular Endocrinology ◽

10.1016/s0303-7207(97)00143-3 ◽

1997 ◽

Vol 133 (1) ◽

pp. 63-71 ◽

Cited By ~ 17

Author(s):

Claude Beaudoin ◽

Martin Bonenfant ◽

Yves Tremblay

Keyword(s):

Cytochrome P450 ◽

Hydroxysteroid Dehydrogenase ◽

Side Chain ◽

Mrna Levels ◽

Side Chain Cleavage ◽

Chain Cleavage ◽

Estradiol 17Β

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Concentrations of cytochrome P450 cholesterol side-chain cleavage enzyme and 3 beta-hydroxysteroid dehydrogenase during prostaglandin F2 alpha-induced luteal regression in cattle

Reproduction Fertility and Development ◽

10.1071/rd9951213 ◽

1995 ◽

Vol 7 (5) ◽

pp. 1213 ◽

Cited By ~ 10

Author(s):

RJ Rodgers ◽

CA Vella ◽

FM Young ◽

XC Tian ◽

JE Fortune

Keyword(s):

Cytochrome P450 ◽

Hydroxysteroid Dehydrogenase ◽

Side Chain ◽

Corpora Lutea ◽

Steroidogenic Enzymes ◽

Rapid Reduction ◽

Plasma Progesterone ◽

Side Chain Cleavage ◽

Prostaglandin F2 Alpha ◽

Chain Cleavage

Prostaglandin F2 alpha (PGF2 alpha)-induced regression of the corpus luteum causes both plasma progesterone concentrations and luteal concentrations of mRNA encoding the steroidogenic enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) to fall in parallel. To investigate the hypothesis that a decline in the concentrations of mRNA encoding steroidogenic enzymes causes plasma progesterone to fall, the luteal concentrations of the enzymes 3 beta-HSD and cytochrome P450 cholesterol side-chain cleavage were measured during induced luteolysis. Holstein heifers were treated with PGF2 alpha (25 mg Lutalyse) on Day 6 or Day 7 of the oestrous cycle and corpora lutea were collected 0 h, 2 h, 12 h, and 24 h later (n = 6, 4, 4, and 4 respectively). Analyses of the steroidogenic enzymes were carried out by Western immunoblotting. The luteal concentrations of both steroidogenic enzymes did not decrease over the 24-h period. It is concluded that, although the concentrations of mRNA encoding steroidogenic enzymes may decline in response to PGF2 alpha, this does not lead to a sufficiently rapid reduction in the concentrations of the enzymes to precede, and thus cause, the decline in plasma progesterone concentrations. Thus, the mechanism for the initial decline in plasma progesterone concentrations during luteolysis is still not known.

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