Serial Measurement of Arterial Plasma Progesterone Levels Throughout Gestation and Parturition in Individual Rats

Bartholomeusz, R. K.; Bruce, Neville; Martin, Cara; Hartmann, PE

doi:10.1530/acta.0.0820436

Cited by 39 publications

(15 citation statements)

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“…1). These findings confirm the conclusions of Bartholomeus et al (1976) that parturition occurs approximately 24 h after the concentration of progesterone has declined to less than 12·0 f1gjl. In four of the six chronically cannulated rats there was a transient halt to the initial decline in plasma progesterone between 40 and 50 h before birth, and then progesterone declined to low levels and birth occurred approximately 24 h later.…”

Section: Discussionsupporting

confidence: 90%

Progressive Changes in Plasma Progesterone, Prolactin and Corticosteroid Levels During Late Pregnancy and the Initiation of Lactose Synthesis in the Rat

Nicholas¹,

Hartmann²

1981

Aust. Jnl. Of Bio. Sci.

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The relationship between progesterone, prolactin, corticosteroids and corticosteroid binding globulin . (CBO) activity in plasma and the initiation of lactation were studied in normal parturient rats, and rats either ovariohysterectomized or Caesarean-sectioned on day 19 of gestation. In chronically cannulated rats the decline in plasma progesterone to low values « 10 p.g/l) in normal parturient rats 20 h before term and in Caesarean-sectioned rats 10--14 h after surgery was closely related to an increase in plasma prolactin. However, in ovariohysterectomized rats the levels of progesterone declined abruptly to 20 p.g/l within 30 min of surgery and prolactin remained low (5 p.g/l) for 4-8 h and then gradually increased during the subsequent 16-18 h. Lactose concentrations in mammary tissue of rats killed at 0, 12, 18. 24, 36 and 48 h after surgery was low « 0·14 mg/g tissue) up to 12 h, and increased to reach maximum values at 36 hand 48 h after surgery in ovariohysterectomized and Caesarean-sectioned rats respectively.The concentration of corticosteroids and CBO capacity in the plasma was 250--550 p.g/l and 250-480 p.g corticosterone bound per litre, respectively, in rats killed during the last 4 days of,gestation. However, both the concentration of corticosteroids and the CBO capacity, within the individual cannulated rats, remained relatively constant during late gestation.These findings support the proposal that progesterone withdrawal is the lactogenic trigger ana suggest the sequential involvement of prolactin. An increase in the concentration of free corticosteroids in late pregnancy and a related stimulatory role in the lactogenic mechanism were not established.

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Section: Discussionsupporting

confidence: 90%

Progressive Changes in Plasma Progesterone, Prolactin and Corticosteroid Levels During Late Pregnancy and the Initiation of Lactose Synthesis in the Rat

Nicholas¹,

Hartmann²

1981

Aust. Jnl. Of Bio. Sci.

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“…In the rat, this decline occurs between about days 20-21 of gestation (48)(49)(50)(51)(52). There is also a steady decline in circulating progesterone titers in fetal rats from day 17 of gestation to the day of birth.…”

Section: Discussionmentioning

confidence: 99%

Plasma Testosterone and Progesterone Titers of Pregnant Rats, Their Male and Female Fetuses, and Neonatal Offspring*

1980

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Testosterone and progesterone titers were determined by RIA in the plasma of pregnant rats and their male and female fetuses from day 17 of gestation through the day of birth and in male and female neonates on days 3 and 5 post partum. Males had significantly higher mean testosterone levels than females from day 18 of gestation through day 5 post partum. Sex differences in plasma testosterone concentrations were greatest in the fetuses on days 18 and 19 of gestation when testosterone levels peaked in the males. Instances in which female fetuses had testosterone titers equal to or greater than their male littermates were found on every day of gestation except day 18. Mean testosterone concentrations in plasma of female fetuses were high throughout gestation (greater than 1000 pcg/ml). Testosterone concentrations decreased in both sexes after birth. Differences between the sexes remained significant, and although there was an overlap in the values for males and females, testosterone concentrations in females exceeded those of their male littermates in only one out of nine pairs of samples on day 5 and in none of seven pairs on day 3 post partum. There were no significant differences in progesterone levels in plasma of males and females, either pre- or postnatally. Progesterone titers changed as a function of days post conception in both the fetuses and their mothers. In the fetuses, progesterone levels declined progressively from day 18 post conception through the day of birth, while in the mother they rose from days 18 to 19 then declined between days 20 and 21 of pregnancy. Fetuses had lower progesterone titers than their mothers. From these data, we conclude that day 18 and possibly day 19 post conception represent a critical period during which the central nervous system of the male is primed by high levels of testosterone. Thereafter, the process of masculinization is completed by exposure to testosterone levels that are relatively low and need not be consistently higher than those of female littermates.

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“…According to Bartholomeusz et al [18] average daily plasma progesterone concentrations in non-pregnant rats may be around 5 ng/ml, rising to 50 ng/ml or more at the start of the third week of pregnancy; the progesterone level varies considerably during the course of a day. In the present study we have used progesterone concentrations which fall into that definition of the normal physiological range, i.e.…”

Section: Discussionmentioning

confidence: 99%

Binding of3H-progesterone by isolated rat islets of Langerhans

et al. 1978

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Summary.Islets of Langerhans isolated from normal female rats have been used in studies of 3H-progesterone uptake by intact islet cells. The intracellular sites which are involved in binding of the hormones have been determined by subcellular fractionation and autoradiography. Uptake of 3H-progesterone into islets occurred in a temperature and concentration dependent manner. The uptake increased rapidly in the first 30 min, and could be partially displaced by addition of excess unlabelled progesterone. 3H-progesterone uptake was lowered by incubation of the islets in the absence of Ca ++, at 0 ° compared to 37 ° C, or to a much lesser extent when islet cycilic AMP levels were raised by addition of 3-isobutyl-1-methylxanthine. However, uptake was unaffected by prior treatment of the islets with neuraminidase or phydroxymercuribenzoate. Differential centrifugation of islets which had previously been incubated with 3H-progesterone showed the highest specific activity of binding in the nuclei and debris fraction. Isolation of a purified nuclear fraction by sedimentation through sucrose solutions confirmed that binding was present in the nuclear component of this heterogeneous fraction, while autoradiographic studies suggested both nuclear and cytosolic localisation of 3H-progesterone. In a separate series of experiments, evidence was obtained for the existence of saturable cytosolic binding of progesterone, and for movement of labelled hormone from the cytosol to the nuclear fraction.It is suggested that, in the islets of Langerhans as in other target tissues, the action of progesterone involves penetration into the cells, binding to a cytosolic receptor protein, and subsequent transfer to the nucleus. The nuclear events which lead to subse-

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Serial Measurement of Arterial Plasma Progesterone Levels Throughout Gestation and Parturition in Individual Rats

Cited by 39 publications

References 0 publications

Progressive Changes in Plasma Progesterone, Prolactin and Corticosteroid Levels During Late Pregnancy and the Initiation of Lactose Synthesis in the Rat

Progressive Changes in Plasma Progesterone, Prolactin and Corticosteroid Levels During Late Pregnancy and the Initiation of Lactose Synthesis in the Rat

Plasma Testosterone and Progesterone Titers of Pregnant Rats, Their Male and Female Fetuses, and Neonatal Offspring*

Binding of3H-progesterone by isolated rat islets of Langerhans

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