The METABOLIC CLEARANCE RATE AND PRODUCTION RATE OF PROGESTERONE AND THE CONVERSION OF PROGESTERONE TO 20α-Hydroxypregn-4-en-3-One IN THE SHEEP

Bedford, Cecelia A.; Harrison, F. A.; Heap, R. B.

doi:10.1677/joe.0.0550105

Cited by 65 publications

(58 citation statements)

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“…This may not, however, reflect abnormal progesterone production since the results could be explained by the fact that anoestrous ewes have a somewhat higher metabolic clearance rate for progesterone than do cyclic animals (Bedford, Harrison & Heap, 1972). In Ewe 0_ (Text-fig.…”

Section: Discussionmentioning

confidence: 97%

Progesterone Levels Following Treatment of Seasonally Anoestrous Ewes With Synthetic Lh-Releasing Hormone

Haresign¹,

Foster²,

Haynes³

et al. 1975

Reproduction

114

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Summary. Plasma progesterone determinations were carried out on blood samples collected daily from Clun Forest ewes during the normal oestrous cycle and also after administration of LH-releasing hormone (LH-RH) during seasonal anoestrus.Levels of plasma progesterone at oestrus ranged from 0\m=.\1to 0\m=.\5 ng/ml and luteal phase levels from 3 to 6 ng/ml. Levels found during seasonal anoestrus were within the range of those observed at oestrus. Following treatment with LH-RH, there was an increase in the plasma LH level in all cases and ovulation occurred in twenty-three out of twenty-seven treated ewes. In the animals which ovulated, the plasma progesterone concentration either remained basal (eighteen animals) or rose to a lower level (<2 ng/ml) than that found during the luteal phase of the cycle.

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Section: Discussionmentioning

confidence: 97%

Progesterone Levels Following Treatment of Seasonally Anoestrous Ewes With Synthetic Lh-Releasing Hormone

Haresign¹,

Foster²,

Haynes³

et al. 1975

Reproduction

114

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“…Therefore, we believe the decreased cytochrome P450 2C and 3A activities in the sodium propionate-supplemented animals compared to the sodium acetate-supplemented animals are most likely due to the effect of elevated insulin concentrations at the time of biopsy. Bedford et al (1972 and1974) reported metabolic clearance rates (volume of blood cleared of progesterone per unit time) for progesterone to be approximately 3.5 to 4.3 l/min in sheep. Splanchnic clearance rate of progesterone could account for 30% of total progesterone metabolism, and 70% to 90% of the total clearance of progesterone in these splanchnic organs was cleared by the liver (Bedford et al, 1974).…”

Section: Discussionmentioning

confidence: 99%

Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

Lemley

Koch

Blemings

et al. 2008

Animal

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Progesterone is essential for maintaining pregnancy, and several authors have suggested that low peripheral concentrations of progesterone may be responsible for high rates of embryonic loss. The primary organ involved in the catabolism of progesterone is the liver, and cytochrome P450 2C and 3A sub-families account for a large proportion of this catabolism. Elucidating a mechanism to decrease progesterone catabolism, thereby increasing embryonic and uterine exposure to progesterone, seems a logical approach to ameliorate high rates of embryonic loss. The objectives of the current experiment were to determine the pattern of insulin secretion after supplementing feed with either sodium acetate or sodium propionate and to determine any association between the differential patterns of insulin secretion with the hepatic activity of cytochrome P450 2C and 3A and progesterone clearance. Sixteen ovariectomized ewes were fed 3 kg/day for 10 days of a diet consisting of 50% corn silage, 38% triticale haylage, 12% soybean meal and 600 ml of 3.5 M sodium acetate (energy control; n 5 8) or 2.0 M sodium propionate (gluconeogenic substrate; n 5 8). Equal portions of the ration (1 kg as-fed basis along with 200 ml of 3.5 M sodium acetate or 2.0 M sodium propionate) were offered three times daily at 0600, 1400 and 2200 h. Concentrations of insulin in plasma were determined immediately before feeding and at 15, 30, 60, 90, 120, 180, 240 and 300 min after feeding. Progesterone clearance from peripheral circulation (ng/ml per min) was measured by giving a 5 mg injection of progesterone into the left jugular vein and collecting blood via the right jugular vein at 0, 2, 4, 6, 8, 10, 15, 20 and 30 min afterwards. Liver biopsies were taken 1 h after feeding to determine cytochrome P450 2C and 3A activities. Insulin concentrations in ewes supplemented with sodium propionate were elevated at 15, 30 and 60 min after feeding compared to the sodium acetate group. Cytochrome P450 2C and 3A activities were decreased 1 h after feeding in the sodium propionate-treated ewes relative to sodium acetate. Insulin appears to down-regulate cytochrome P450 activity, which could be used to decrease the catabolism of progesterone during early gestation, thereby increasing peripheral concentrations of progesterone and, consequently, embryonic exposure to progesterone.

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“…It seems improbable that PGF-2a stimulated myometrial contractions in our preparations in view of the large amount of fluid that accumulated in the uterus, but the effect may have been inhibited by the circulating level of progesterone normally found in pregnancy (Bedford, Harrison & Heap, 1972).…”

Section: Discussionmentioning

confidence: 84%

Production, chemical composition and prostaglandin F-2 content of uterine fluid in pregnant sheep

Harrison¹,

Heap²,

Poyser³

1976

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Summary. A uterine pouch was prepared surgically in ewes before mating to study the production and chemical composition of uterine secretions during pregnancy. Pregnancy was established in 6 sheep and in the first 55 days uterine fluid was present in small amounts (<5 ml), whereas between 109 days post coitum and 3 days post partum the volume ranged from 90 to 775 ml.The chemical composition of uterine fluid in pregnancy differed from that of plasma especially in respect of its high concentration of total calcium (up to 83\m=.\5mM) and prostaglandin (PG) F-2\g=a\(up to 1500 ng/ml). Progesterone was implicated as an important endocrine factor since uterine fluid (188 ml) with a high concentration of total calcium (53\m=.\5mM) and PGF-2\g=a\(235 ng/ml) was recovered from a non-pregnant sheep treated with progesterone for 115 days.

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The METABOLIC CLEARANCE RATE AND PRODUCTION RATE OF PROGESTERONE AND THE CONVERSION OF PROGESTERONE TO 20α-Hydroxypregn-4-en-3-One IN THE SHEEP

Cited by 65 publications

References 0 publications

Progesterone Levels Following Treatment of Seasonally Anoestrous Ewes With Synthetic Lh-Releasing Hormone

Progesterone Levels Following Treatment of Seasonally Anoestrous Ewes With Synthetic Lh-Releasing Hormone

Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

Production, chemical composition and prostaglandin F-2 content of uterine fluid in pregnant sheep

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