Acetate and plasma cholesterol as progesterone precursors in the intact ovary of the Day-16 pregnant rat

Swann, R. T.; Bruce, Neville

doi:10.1530/jrf.0.0770655

Cited by 7 publications

(5 citation statements)

References 23 publications

(29 reference statements)

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“…Blood-borne cholesterol appears to be physiologically important for luteal func¬ tion in the cow, because elevated serum cholesterol values result in increased progesterone concen¬ trations during the luteal phase (Talavera et ai, 1985). Circulating cholesterol is probably the preferred substrate, as opposed to de-novo synthesis of cholesterol, in many species (see review by Gwynne & Strauss, 1982;Swann & Bruce, 1986).…”

Section: Introductionmentioning

confidence: 99%

Regulation of steroidogenesis and cholesterol synthesis by prostaglandin F-2 and lipoproteins in bovine luteal cells

Pate

Condon

1989

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Bovine luteal cells can utilize low density lipoprotein (LDL) or high density lipoprotein (HDL) as a source of cholesterol for steroidogenesis, and administration of PGF-2 alpha in vitro suppresses lipoprotein utilization. The objective of this study was to examine the mechanism by which PGF-2 alpha exerts this effect. Cultured bovine luteal cells received 0.25 microCi[14C]acetate/ml, to assess rates of de-novo sterol and steroid synthesis, with or without lipoproteins. Both LDL and HDL enhanced progesterone production (P less than 0.01), but caused a significant reduction in the amount of radioactivity in the cholesterol fraction. PGF-2 alpha treatment inhibited the increase in lipoprotein-induced progesterone synthesis (P less than 0.01), but did not prevent the reduction in de-novo cholesterol synthesis brought about by LDL or HDL. PGF-2 alpha alone reduced cholesterol synthesis (P less than 0.01), but it was not as effective as either LDL or HDL. Both lipoproteins and PGF-2 alpha also decreased the amount of radioactivity in the progesterone fraction (P less than 0.01), and the effect of PGF-2 alpha was similar to that of the lipoproteins. It is concluded that lipoproteins can enhance progesterone production and also suppress de-novo cholesterol synthesis in bovine luteal cells, but only the former effect of lipoproteins is inhibited by PGF-2 alpha. Therefore, it is suggested that PGF-2 alpha allows entry of lipoprotein cholesterol into the cell, but prevents utilization for steroidogenesis. In addition, PGF-2 alpha alone can suppress cholesterol synthesis, as well as decrease conversion of cholesterol to progesterone.

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Section: Introductionmentioning

confidence: 99%

Regulation of steroidogenesis and cholesterol synthesis by prostaglandin F-2 and lipoproteins in bovine luteal cells

Pate

Condon

1989

Reproduction

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“…A second explanation may relate to a change in the supply of cholesterol for steroidogenesis, since the de novo synthesis of cholesterol via the 3-hydroxy-3-methylgutaryl coenzyme A reductase enzyme also occurs on the SER (Azhar et al, 1985). Although studies in vivo have shown that this route of cholesterol supply for luteal steroidogenesis is quantitatively insignificant at day 16 of rat pregnancy (Swann and Bruce, 1986), it is not clear how much cholesterol is derived via this conversion on day 22. If the amount of de novo cholesterol synthesis does change with advancing pregnancy, it could mask any relationship that might exist between luteal ultrastructure and the amount of steroid secreted.…”

Section: Discussionmentioning

confidence: 99%

Quantitative changes in steroidogenic organelles in the corpus luteum of the pregnant rat in relation to progestin secretion on day 16 and in the morning and afternoon of day 22

1991

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The present study was carried out to determine whether the major steroidogenic organelles of luteal cells quantitatively reflect variations in ovarian steroid secretion rates during pregnancy in the rat. Assessments were made on day 16 and in the morning (AM) and afternoon (PM) of day 22 (term is day 23). Ovarian steroidogenesis differs both quantitatively and qualitatively between these stages of pregnancy, so together they provide an ideal physiological model to study structural-functional relationships in the ovary. Corpora lutea of five rats were examined at each stage after progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP) secretion rates had been determined by a venous outflow technique. Total progestin secretion (progesterone plus 20 alpha-OHP) fell from 32.5 +/- 5.2 to 9.8 +/- 1.2 micrograms/hr per ovary (mean +/- SEM) between day 16 and day 22 AM but then increased to 22.6 +/- 1.4 micrograms/hr per ovary by day 22 PM. The total volume of luteal cell cytoplasm was slightly greater at day 22 AM and PM than at day 16. Similarly, the volumes of smooth endoplasmic reticulum (SER), lipid droplets, and membrane-bound granules all increased, but the volume of mitochondria decreased slightly. In contrast, the surface areas of SER and the inner and outer mitochondrial membranes did not change between day 16 and day 22 AM but then increased substantially by day 22 PM. Therefore, steroid secretion rates per unit area of steroidogenic membrane showed no consistent pattern over the stages examined.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Samples for steroid assay were stored at -10°C until assayed. At the end of the experiments both ovaries were removed and the corpora lutea of pregnancy were separated from those of the previous cycles as previously described (Swann & Bruce, 1986) and analysed for progestagen and total cholesterol content.…”

Section: Methodsmentioning

confidence: 99%

“…Analysis. Progesterone and 20a-dihydroprogesterone determinations were carried out by RIA as previously described (Swann & Bruce, 1986). Intra-and inter-assay coefficients of variation were 61% and 100% respectively for progesterone and 4-5% and 11 4% respectively for 20a-dihydroprogesterone.…”

Section: Methodsmentioning

confidence: 99%

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Oxygen consumption, carbon dioxide production and progestagen secretion in the intact ovary of the Day-16 pregnant rat

Swann

Bruce²

1987

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Arterial and venous blood gases were measured in the ovary of the Day-16-pregnant rat by a Van Slyke manometric technique. Concurrent observations of progestagen concentrations were also made to determine rates of hormone secretion. The oxygen consumption was 196.5 +/- 28.4 ml/min per kg ovarian tissue (mean +/- s.e.m., n = 8) which is amongst the highest recorded from any organ. Carbon dioxide production was 149.8 +/- 36.6 ml/min per kg ovarian tissue (n = 5) and the respiratory quotient was 0.756 +/- 0.023 (n = 5), indicating that lipids are the major energy substrate used by the ovary. The rates of progestagen secretion were 2.12 +/- 0.37 and 0.42 +/- 0.10 nmol/min per ovary for progesterone and 20 alpha-dihydroprogesterone, respectively, and were not related to oxygen consumption. Less than 1.5% of the oxygen consumed was used in the essential conversion of cholesterol to pregnenolone, the immediate precursor of progesterone.

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Acetate and plasma cholesterol as progesterone precursors in the intact ovary of the Day-16 pregnant rat

Cited by 7 publications

References 23 publications

Regulation of steroidogenesis and cholesterol synthesis by prostaglandin F-2 and lipoproteins in bovine luteal cells

Regulation of steroidogenesis and cholesterol synthesis by prostaglandin F-2 and lipoproteins in bovine luteal cells

Quantitative changes in steroidogenic organelles in the corpus luteum of the pregnant rat in relation to progestin secretion on day 16 and in the morning and afternoon of day 22

Oxygen consumption, carbon dioxide production and progestagen secretion in the intact ovary of the Day-16 pregnant rat

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