PLASMA CORTICOSTERONE CONCENTRATIONS AND PITUITARY PROLACTIN CONTENT IN LATE PREGNANCY AND THEIR WITHIN-DAY FLUCTUATIONS IN THE RAT

1974 ◽  
Vol 61 (1) ◽  
pp. 21-28 ◽  
Author(s):  
KATUAKI ÔTA ◽  
TAKAO ÔTA ◽  
AKIRA YOKOYAMA
Keyword(s):  
Late Pregnancy ◽  
Plasma Corticosterone ◽  
Prolactin Secretion ◽  
Corticosterone Concentration ◽  
Corticosterone Secretion ◽  
Prolactin Content ◽  
Pituitary Prolactin

SUMMARY Levels of plasma corticosterone and of pituitary prolactin were studied in the mornings (10.00–10.30 h) and evenings (17.00–18.00 h) during the last week of pregnancy in the rat. Morning levels of plasma corticosterone started to rise on day 19 and reached a peak on day 21. The concentration of corticosterone in plasma on the morning of day 21 was about 2·3 times higher than that on day 15. Both content and concentration of prolactin in the pituitary began to fall on the morning of day 19 of pregnancy and the minimum values for both content and concentration were reached on the morning of day 21. Plasma corticosterone concentration and pituitary prolactin content measured in the evening, however, remained high throughout the period examined and there were no appreciable changes in the levels at the different stages of pregnancy. The results obtained on day 22 of pregnancy, the expected day of parturition, indicated that a surge of pituitary prolactin secretion and a temporary depression of corticosterone secretion occurred at about the time of parturition.

Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat

1985 ◽  
Vol 107 (3) ◽  
pp. 325-329 ◽  
Author(s):  
H. Cohen ◽  
I. Sabbagh ◽  
P. Guillaumot ◽  
J. Bertrand
Keyword(s):  
Adult Male ◽  
Physiological Saline ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Saline Control ◽  
Plasma Prolactin ◽  
Synthesis Inhibitor ◽  
Nude Rat ◽  
Prolactin Content ◽  
Pituitary Prolactin

ABSTRACT In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat. J. Endocr. (1985) 107, 325–329

Adrenocortical responses of ducks to treadmill exercise

1982 ◽  
Vol 94 (1) ◽  
pp. 141-146 ◽  
Author(s):  
S. Harvey ◽  
J. G. Phillips
Keyword(s):  
Treadmill Exercise ◽  
Plasma Corticosterone ◽  
Pretreatment Level ◽  
Corticosterone Concentration ◽  
Domestic Ducks ◽  
Corticosterone Secretion ◽  
Corticosterone Response ◽  
Response To Exercise ◽  
Adrenocortical Responses ◽  
Stationary Control

The influence of treadmill exercise on corticosterone secretion has been determined in domestic ducks. In birds unused to such exercise the concentrations of plasma corticosterone were markedly increased (> fourfold) after 15 or 30 min of treadmill exercise (1·1 km/h at 3 ° grade) and the level remained high (between 30 and 40 ng/ml) throughout 90 min of exercise. This increase in corticosterone secretion accompanied a similar increase in colon temperature and was independent of the plasma glucose level. After exercise the corticosterone concentration declined to the pretreatment level within 60 min of recovery. In birds used to the exercise the corticosterone response to a standard (30 min) period of exercise was diminished (by 77·6% in comparison with untrained birds and was no greater than the response (1·7-fold) in stationary control birds after handling and bleeding. The diminution of the corticosterone response to exercise may be due to the trained birds becoming fitter and better able to perform the work involved.

Effect of adenosine analogues on plasma corticosterone concentration in rats

1992 ◽  
Vol 127 (5) ◽  
pp. 471-475 ◽  
Author(s):  
Edmund Przegaliński ◽  
Bogusława Budziszewska ◽  
Anna Grochmal
Keyword(s):  
Adenosine Receptor ◽  
Corticosterone Level ◽  
Plasma Corticosterone ◽  
Receptor Antagonists ◽  
Corticosterone Concentration ◽  
Adenosine Analogues ◽  
Negative Results ◽  
Corticosterone Secretion ◽  
Corticosterone Response ◽  
Pharmacological Blockade

In this study we examined the effect of the adenosine analogues: N6-cyclohexyladenosine, L-N6-phenylisopropyladenosine and 5′-N-ethylcarboxamidoadenosine on the plasma corticosterone concentration in rats. It was found that N6-cyclohexyladenosine (0.1–3.0 mg/kg), L-N6-phenylisopropyladenosine (0.1–1.0 mg/kg) and 5′-N-ethylcarboxamidoadenosine (0.01–1.0 mg/kg) dose-dependently increased the plasma corticosterone level. The effects of N6-cyclohexyladenosine (0.1 mg/kg) and L-N6-phenylisopropyladenosine (0.1 mg/kg) were completely blocked in animals pretreated with dexamethasone (3 × 1 mg/kg), as well as in animals with a pharmacological blockade of the release of hypothalamic corticotropin-releasing factor induced by chloropromazine (10 mg/kg), morphine (20 mg/kg) and nembutal (25 mg/kg), whereas the corticosterone response to 5′-N-ethylcarboxamidoadenosine (0.01 mg/kg) was blocked in dexamethasone-pretreated rats only. On the other hand, the adenosine receptor antagonists: 8-(p-sulfophenyl)-theophylline (30 mg/kg), 8-phenyltheophylline (10 and 30mg/kg), 1,3-dipropyl-8-(2-amino-4-chloro)-phenylxanthine (1 and 3 mg/kg) and 1,3-dipropyl-7-methylxanthine (1 mg/kg) did not affect the corticosterone response to N6-cyclohexyladenosine, L-N6-phenylisopropyladenosine or 5′-N-ethylcarboxamidoadenosine. The obtained results indicate that N6-cyclohexyladenosine and L-N6-phenylisopropyladenosine stimulate the corticosterone secretion at the hypothalamic level, whereas 5′-N-ethylcarboxamidoadenosine is likely to act at the pituitary level. Although the effects produced by the adenosine analogues show that both A1 and A2 receptors are involved in the corticosterone response, negative results of the interaction studies with adenosine receptor antagonists indicate that further experiments are necessary to elucidate this problem.

THE EFFECTS OF HYPOPHYSECTOMY ON ADRENOCORTICAL FUNCTION IN THE DUCK (ANAS PLATYRHYNCHOS)

1971 ◽  
Vol 49 (3) ◽  
pp. 437-457 ◽  
Author(s):  
E. L. BRADLEY ◽  
W. N. HOLMES
Keyword(s):  
Mammalian Species ◽  
Compartment Model ◽  
Liver Glycogen ◽  
Plasma Corticosterone ◽  
Adrenocortical Function ◽  
Metabolic Clearance ◽  
General Effect ◽  
Corticosterone Concentration ◽  
Peripheral Plasma ◽  
Corticosterone Secretion

SUMMARY The general effect of chronic hypophysectomy on organ and body weights, liver glycogen, blood glucose, peripheral plasma corticosterone concentrations, and blood pressure in the duck were similar to those described for several mammalian species. The disappearance and distribution of radioactivity after the administration of [1,2-3H]corticosterone and [1,2-3H]aldosterone was studied according to a single compartment model system. When compared with sham-operated ducks, the apparent volumes of distribution and the biological half-lives of radioactivity in hypophysectomized ducks were significantly increased, and the estimated metabolic clearance rates of [1,2-3H] corticosterone and [1,2-3H]aldosterone were significantly decreased. The patterns of distribution of radioactivity and the rate of metabolism of both hormones returned towards normal when the chronically hypophysectomized ducks were treated with corticotrophin (ACTH). Fourteen days after hypophysectomy the peripheral plasma concentration of corticosterone and the estimated rate of corticosterone secretion by the adrenal fell to 10 and 4%, respectively, of the values observed in sham-operated birds. Examinations of the peripheral plasma corticosterone concentration during the first 30 min after the removal of the adenohypophysis indicated a mean biological half-life for endogenous corticosterone of 13·7 min. The rates of appearance of radioactivity in the bile, intestine and cloaca of the hypophysectomized birds suggested substantial declines in the rates of aldosterone and corticosterone metabolism. These declines could not be accounted for by the reduced rate of glomerular filtration in the hypophysectomized bird. Replacement therapy with ACTH restored the excretory patterns of both steroids towards normal. The quantitative similarities between the effects of hypophysectomy in the duck and several mammalian species make it unnecessary to postulate either a high degree of adrenal autonomy or an extrahypophysial source of ACTH in the control of adrenocortical function in the duck.

MATERNAL AND FOETAL CORTICOSTERONE LEVELS DURING LATE PREGNANCY IN RATS

1975 ◽  
Vol 65 (3) ◽  
pp. 347-352 ◽  
Author(s):  
J. P. DUPOUY ◽  
H. COFFIGNY ◽  
S. MAGRE
Keyword(s):  
Late Pregnancy ◽  
Maternal Plasma ◽  
Plasma Corticosterone ◽  
Pregnant Rats ◽  
Corticosterone Concentration

SUMMARY Adrenal and plasma corticosterone levels were determined in rat foetuses and in intact or adrenalectomized mothers during late pregnancy. Foetal adrenal and plasma corticosterone concentrations reached a peak on day 19 of pregnancy, while maternal plasma corticosterone increased on day 18 and remained high until parturition. From day 18, mothers adrenalectomized on day 14 had corticosterone levels similar to those of intact pregnant rats. At every stage of gestation (except day 21) plasma corticosterone levels were higher in the foetuses than in the mothers. The corticosterone concentration in the maternal plasma correlated with the number of live foetuses during the last 3 days of gestation. These results suggest that corticosterone can cross the placenta from foetus to mother as early as day 18 and that the foetus contributes to the maternal corticosterone pool after day 18.

PROLACTIN RELEASE IN PARENT RING DOVES AFTER BRIEF EXPOSURE TO THEIR YOUNG

1979 ◽  
Vol 82 (1) ◽  
pp. 127-130 ◽  
Author(s):  
J. D. BUNTIN
Keyword(s):  
Sex Differences ◽  
Pituitary Gland ◽  
Environmental Regulation ◽  
Prolactin Secretion ◽  
Radioreceptor Assay ◽  
Prolactin Release ◽  
The Third ◽  
Prolactin Content ◽  
Pituitary Prolactin ◽  
Ring Doves

SUMMARY A pigeon crop sac radioreceptor assay was used to measure changes in pituitary prolactin levels in parent ring doves of both sexes on the third day after hatching of their young. After a deprivation of 17 h from the squabs, exposure to a 3-day-old squab for 1 h resulted in a significant decrease in the prolactin content of the pituitary gland as compared with levels obtained in control birds deprived of their young for 18 h. No significant sex differences in prolactin levels were observed in either group. Because exposure to the young also promotes prolactin-induced crop sac growth, it appears probable that the squab-induced decrease in prolactin content of the pituitary gland reflects the release of prolactin into the circulation. Accordingly, the environmental regulation of prolactin secretion in parent ring doves appears similar to that observed in lactating mammals.

Autoregulation of rat pituitary prolactin secretion demonstrated by a new perfusion method

1982 ◽  
Vol 242 (4) ◽  
pp. E226-E233
Author(s):  
H. A. Zacur ◽  
W. E. Mitch ◽  
J. E. Tyson ◽  
P. T. Ostrow ◽  
G. V. Foster
Keyword(s):  
Prolactin Secretion ◽  
Renal Capsule ◽  
In Vitro Perfusion ◽  
Prolactin Release ◽  
Rat Pituitary ◽  
Inbred Rats ◽  
Pituitary Glands ◽  
Prolactin Content ◽  
Pituitary Prolactin

Regulation of prolactin secretion was investigated by perfusing rat pituitaries in vitro. Two pituitary glands from inbred rats were transplanted beneath the renal capsule of a third recipient rat. Three weeks later, the transplanted kidney was removed and perfused in vitro with a defined cell-free medium. Normal renal function was maintained during perfusion, and cell morphology of the transplants remained unchanged as assessed by electron microscopy. Pituitary prolactin content did not change after 120 min of perfusion despite release of approximately 10 micrograms of hormone. Thyrotropin-releasing hormone (10 ng/ml) did not stimulate prolactin release; dopamine (20 ng/ml) rapidly, but transiently inhibited prolactin release; bromocriptine (20 ng/ml) rapidly and persistently inhibited prolactin release; haloperidol (100 ng/ml) blocked the inhibition by dopamine or bromocriptine, but when given alone inhibited prolactin release. Finally, prolactin release was also inhibited by the presence of 100 and 200 ng/ml, but not 50 ng/ml of NIAMDD RP-1 rat prolactin. It is concluded that in vitro perfusion of transplanted rat pituitaries provides a new model for studying the direct effect of agents on the secretion of prolactin from the pituitary and that rat prolactin and/or its metabolites directly inhibit pituitary prolactin secretion.

Role of Oxytocin in Prolactin Secretion during Late Pregnancy

2017 ◽  
Vol 106 (4) ◽  
pp. 324-334 ◽  
Author(s):  
Carlos M. Villegas-Gabutti ◽  
Gisela E. Pennacchio ◽  
Laura Vivas ◽  
Graciela A. Jahn ◽  
Marta Soaje
Keyword(s):  
Elevated Serum ◽  
Late Pregnancy ◽  
Prolactin Secretion ◽  
Rt Pcr ◽  
Stimulatory Action ◽  
Paraventricular Nuclei ◽  
Dopaminergic Tone ◽  
Pituitary Prolactin ◽  
Supraoptic Nuclei

Background/Aims: During late pregnancy, the blockade of progesterone action by mifepristone (Mp) treatment induces a dopaminergic tone fall that enables naloxone (NAL) administration to release pituitary prolactin (PRL). We determined whether oxytocin (OT), which stimulates PRL secretion acting directly on anterior pituitary lactotrophs, mediates the stimulatory action of Mp and NAL on PRL secretion during late pregnancy. Methods: On day 19 of pregnancy, circulating and pituitary OT and PRL levels were measured by radioimmunoassay, 10, 20, and 30 min after NAL (given at 17:30 h) in rats pretreated with Mp (at 08:00 h). Pituitary OT receptor (OTR) expression in Mp-treated rats was evaluated by RT-PCR. Activation of OT neurons in Mp-NAL-treated rats was measured counting double immunoreactive neurons for Fos and OT (Fos-OT-ir) in supraoptic nuclei (SON), and medial (PaMM) and lateral magnocellular divisions of paraventricular nuclei. Results: Elevated serum OT and decreased pituitary OT were observed 10 min after NAL administration in both vehicle- and Mp-treated rats. This PRL increase was prevented by previous i.p. administration of an OTR antagonist, but intracerebroventricular OT administration was ineffective. Mp increased pituitary OTR expression at 18:00 h. Only Mp-NAL increased Fos-OT-ir neurons in the PaMM and SON. Conclusions: These findings suggest that PRL secretion induced by Mp-NAL treatment is preceded by OT release. These results, together with the activation of hypothalamic OT neurons and the higher expression of pituitary OTR, support the hypothesis that, during late pregnancy, OT may act at the pituitary level to facilitate PRL secretion if the inhibitory action of progesterone is blocked.

scholarly journals The effects of fasting on plasma corticosterone kinetics in rats

1991 ◽  
Vol 66 (1) ◽  
pp. 117-127 ◽  
Author(s):  
C. J. H. Woodward ◽  
G. R. Hervey ◽  
R. E. Oakey ◽  
E. M. Whitaker
Keyword(s):  
Binding Capacity ◽  
Plasma Corticosterone ◽  
Corticosterone Concentration ◽  
Corticosterone Secretion ◽  
Fractional Clearance ◽  
Anaesthetized Rats ◽  
Males And Females ◽  
The Mean ◽  
Rate Limiting ◽  
Secretion Rates

Plasma corticosterone clearance in anaesthetized rats was measured from the disappearance of radioactivity after a bolus injection of [3H]corticosterone. Mean fractional clearance rates were significantly (P < 0.05) reduced after a 48 h fast, by 32 and 22% for males and females respectively. Plasma corticosterone concentrations were increased by fasting in both sexes. Corticosterone secretion rates, calculated as the product of fractional clearance and plasma corticosterone concentration, did not differ between fed and fasted groups in either sex. The mean activity (U/liver) of the rate-limiting enzyme for corticosterone degradation, hepatic 4,5-dihydrocorticosterone:NADP+ Δ4-oxidoreductase, was significantly reduced by 51 and 78% after fasting in males and females respectively. This was due to changes in both the soluble and microsomal forms of the enzyme. The binding capacity of corticosterone-binding globulin in plasma was significantly reduced by fasting in females (P < 0.001), but was not altered in males. The results suggest that reduced hormone clearance is the dominant cause of fasting hypercorticosteronaemia in the rat.

Sign in / Sign up

Export Citation Format

Share Document