Tihe Concentrations of Progesterone, Estrone and Estradiol-17β in the Plasma of Pregnant Rabbits

Challis, John; Davies, I. John; Ryan, Kenneth J.

doi:10.1210/endo-93-4-971

Cited by 238 publications

(96 citation statements)

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“…Kuhn (1969) and Denamur (1971) have suggested that progesterone acts as a repressor of milk biosynthesis before the onset of lactation. In the rabbit, the initial decline in the concentration of plasma progesterone occurs by day 21 of pregnancy (Denamur, 1971;Challis et al, 1973) which coincides with the first lactogenic stimulus. There do not appear to be any reports of changes in the plasma concentration of prolactin in the rabbit during lactogenesis, but it seems likely that prolactin is involved as well as cortisol.…”

Section: Discussionmentioning

confidence: 99%

Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Mellenberger

Bauman

1974

Biochemical Journal

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1. Mammary tissue, obtained from rabbits at various stages of pregnancy and lactation, was used for tissue-slice incubations to measure the rate of lactose biosynthesis and for relevant enzymic activity measurements. A biphasic adaptation in the rate of lactose synthesis and in the RNA concentration was noted during lactogenesis. 2. The first increase in the rate oflactose biosynthesis occurred between days 15 and 24 ofpregnancy. A second substantial increase was noted immediately postpartum. The overall rate of lactose biosynthesis increased 12-fold from day 24 of pregnancy to day 15 of lactation postpartum, and then decreased from 15 to 22 days post partum. 3. The RNA concentration/g wet wt. of tissue and the ratio of RNA/DNA closely represented the biphasic ability of the mammary-tissue slice to synthesize lactose. 4. Increases in the activities of UDP-glucose 4-epimerase (EC 5.1.3.2) and lactose synthase (EC 2.4

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Section: Discussionmentioning

confidence: 99%

Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Mellenberger

Bauman

1974

Biochemical Journal

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“…Progesterone begins to increase on d 2-3, increases steadily until d 12-14 and drops sharply on d 28-29 before parturient activity (Challis et al, 1973;Thau and Lanman, 1975;Zoldag et al, 1988 (Fortun, 1993). Thus, an effect of the lower progesterone concentration in the high foetal mortality observed in simultaneously pregnant and lactating does may be hypothesized.…”

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confidence: 99%

Influence of progesterone supplementation on foetal survival in concurrently pregnant and lactating does

Fortun¹

1994

Reprod. Nutr. Dev.

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Summary ― An experiment was conducted to assess the influence of progesterone levels on late foetal mortality (second half of gestation) in concurrently pregnant and lactating does. All the females were mated within 12 h of parturition (d 0), and slaughtered on d 28 to study reproductive performance and body composition. Females were allowed to lactate 10 young and received either 2 progesterone implants (group P, n = 29) or 2 empty implants (group C, n = 29) on d 7. The feed intake, the live-weight variations of females during gestation, the growth of suckling litters, as well as the foetal weight and body composition of the does at slaughter, were similar in both groups. The concentration of progesterone was higher in group P than in C on d 16 and 25 (P < 0.01 The ovulation rate and late foetal mortality were similar in both groups but the early mortality was lower (12.3 vs 21.2%; P < 0.05) and the total number of foetuses on d 28 (live + resorbed + dead) was higher (9.8 vs 8.7; P < 0.05) in group P. These results indicate that progesterone supplementation improves early foetal survival but cannot increase late foetal survival in concurrently pregnant and lactating does.

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“…However, progesterone alone maintained pregnancy in the majority of ovariectomized, adrenalectomized does, leaving any significant role for oestrogen in considerable doubt. The experiments of Kwun and Emmens (1974), however, did not extend beyond killing and examination on day 30, just prior to expected birth, and the assertion that oestrogen might assist in the birth processes (Schofield 1957;Davies and Ryan 1972;Waynforth and Robertson 1972;Challis et al 1973) was not examined. In addition, the suspicion that 20cx-dihydroprogesterone (20cx-hydroxypreg-4-en-3-one, formerly known as 20cx-hydroxyprogesterone) might have a special function early in pregnancy (Hilliard et al 1967) was not explored.…”

Section: Introductionmentioning

confidence: 99%

Further Observations on Hormonal Support of Pregnancy in the Ovariectomized Rabbit

Kwun¹,

Emmens²

1975

Aust. Jnl. Of Bio. Sci.

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While the necessity for progesterone administration throughout pregnancy in the ovariectomized rabbit is not questioned, the roles of 20oc-dihydroprogesterone and oestradiol are stilI in doubt.20oc-dihydroprogesterone was shown to be a weak inducer of implantation with less than one-tenth the potency of progesterone. The significance of its high level of production on the day after mating remains obscure.In combination with the earlier results of Kwun and Emmens (1974), further work with oestradiol suggests that at no stage is it clearly needed for successful maintenance of pregnancy. However, in low doses (0·125-O·2Ilg/day prior to implantation, 0·2 rising to 1·6Ilg, or remaining at 0·2Ilg/day thereafter) it produced slight but sometimes significant improvements in implantation and foetal development percentages.Birth processes were abnormal if progesterone injections were continued beyond day 29. Foetuses were most frequently retained in utero or born dead after a somewhat prolonged pregnancy. The cessation of injections on day 29, whether or not a low dosage of 0·2 Ilg of oestradiol per day were continued, resulted in 94-98 % normal parturition, but the percentage of live births was stilI significantly below that of controls unless oestradiol was given.

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Tihe Concentrations of Progesterone, Estrone and Estradiol-17β in the Plasma of Pregnant Rabbits

Cited by 238 publications

References 0 publications

Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Influence of progesterone supplementation on foetal survival in concurrently pregnant and lactating does

Further Observations on Hormonal Support of Pregnancy in the Ovariectomized Rabbit

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