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.

Prolactin secretion and dopamine receptors of the MtTW15 transplantable pituitary tumour

1982 ◽  
Vol 94 (3) ◽  
pp. 347-NP ◽  
Author(s):  
M. J. Cronin ◽  
D. A. Keefer ◽  
C. A. Valdenegro ◽  
L. G. Dabney ◽  
R. M. MacLeod
Keyword(s):  
Pituitary Gland ◽  
Dopamine Receptors ◽  
Anterior Pituitary ◽  
Pituitary Tumour ◽  
Prolactin Secretion ◽  
Tumour Cells ◽  
Dopamine Antagonist ◽  
Cell Column ◽  
Prolactin Release

The MtTW15 transplantable pituitary tumour grown in rats was tested in vitro for the ability of dopamine agonists to affect prolactin secretion and for the existence of dopamine receptors. Prolactin release from enzymatically dispersed cells and non-enzymatically treated tissue fragments of both the tumour and the anterior pituitary gland was determined in a cell perifusion column apparatus. Dopamine (0·1–5 μmol/l), bromocriptine (50 nmol/l) and the dopamine antagonist haloperidol (100 nmol/l) had no effect on prolactin release from the tumour cells. In contrast, dopamine (500 nmol/l) inhibited prolactin secretion from normal anterior pituitary cells in a parallel cell column and haloperidol blocked this inhibition. Although oestrogen treatment in vivo stimulated prolactin release in vitro when the tumour was removed and studied in the cell column, oestrogen had no effect on the inability of dopamine to modify the prolactin secretion. Growth hormone release from the tumour cells was not affected by dopamine. Although MtTW15 cells were refractory to dopaminergic inhibition of prolactin release, the dopamine receptors present in tumour homogenates were indistinguishable from the dopamine receptors previously defined in the normal anterior pituitary gland. The binding of the dopamine antagonist [3H]spiperone to the tumour was saturable (110 fmol/mg protein), of high affinity to one apparent class of sites (dissociation constant = 0·12 nmol/l), reversible and sensitive to guanine nucleotides. The pharmacology of the binding was defined in competition studies with a large number of agonists and antagonists. From the order of potency of these agents, a dopaminergic interaction was apparent. We conclude that the prolactin-secreting MtTW15 tumour cells appear to be completely unresponsive to dopamine or to the potent dopamine agonist bromocriptine, in spite of apparently normal dopamine receptors in the tumour.

Cell-density dependence of the rate of prolactin secretion from perifused rat anterior pituitary cells

1983 ◽  
Vol 97 (2) ◽  
pp. 221-228 ◽  
Author(s):  
A. M. Bentley ◽  
M. Wallis
Keyword(s):  
Density Dependence ◽  
Cell Density ◽  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Cells ◽  
The Third ◽  
Pituitary Glands ◽  
Prolactin Content ◽  
Perifusion System

Anterior pituitary glands from female rats were dispersed enzymically in the absence of dopamine. Dispersed cells (106–107) were layered onto columns containing Bio-Gel P-2 and were then perifused for 3 h with Dulbecco's Modified Eagle's Medium. The prolactin content of the perifusate and cell homogenates was determined by radioimmunoassay. Prolactin secretion during the third hour of perifusion increased as the loading of cells increased. However, the increase was not linear, and when secretion rate per 106 cells was calculated it was found that increased loading decreased the rate, which fell to a plateau of 1·3 ± 0·1 (s.e.m.) ng/min per 106 cells at a loading of about 8 × 106 cells from 3·8 ± 0·1 ng/min per 106 cells for a loading of 106 cells. This cell-density dependence of the rate of prolactin secretion in the perifusion system may be due to intercellular contact since the isolation of the tissue removes the influence of hypothalamic factors, while localized build up of prolactin (potentially causing direct autoregulation on the lactotroph) seems unlikely because of the continuous flow of medium.

2-HYDROXYOESTRADIOL INHIBITS PROLACTIN RELEASE FROM THE SUPERFUSED RAT PITUITARY GLAND

1981 ◽  
Vol 90 (3) ◽  
pp. 315-322 ◽  
Author(s):  
ELIZABETH A. LINTON ◽  
NICKI WHITE ◽  
OFELIA LIRA DE TINEO ◽  
S. L. JEFFCOATE
Keyword(s):  
Pituitary Gland ◽  
Prolactin Secretion ◽  
Male Rat ◽  
Prolactin Release ◽  
Rat Pituitary ◽  
Lh Release

The effects of 2-hydroxyoestradiol (2OH-OE2), dopamine, oestradiol-17β and 2OH-OE2 plus dopamine on prolactin and LH release from the male rat pituitary gland were examined in vitro. 2-Hydroxyoestradiol reduced prolactin secretion by 51% at 10−10 mol/l and by 34% at 10−7 mol/l, while oestradiol-17β had no effect at these doses. Dopamine alone (5 × 10−7 mol/l) decreased prolactin released by 58%, 2OH-OE2 plus dopamine produced a similar inhibition of 60%. No significant effect on LH release was observed throughout.

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

ONSET OF OESTROGEN-INDUCED PROLACTIN SECRETION AND DNA SYNTHESIS BY THE RAT PITUITARY GLAND

1977 ◽  
Vol 72 (1) ◽  
pp. 35-39 ◽  
Author(s):  
JOAN JACOBI ◽  
H. M. LLOYD ◽  
J. D. MEARES
Keyword(s):  
Dna Synthesis ◽  
Pituitary Gland ◽  
Prolactin Secretion ◽  
Male Rat ◽  
Serum Prolactin ◽  
Rat Pituitary ◽  
The Times ◽  
Pituitary Prolactin

SUMMARY The times of onset of oestrogen-induced prolactin secretion and DNA synthesis were studied in the pituitary gland of the male rat. At intervals from 3 to 96 h after injection of 10 mg diethylstilboestrol dipropionate, serum and pituitary prolactin concentrations were measured by radioimmunoassay and pituitary DNA synthesis by incorporation of [3H]thymidine in vitro. Serum prolactin was raised significantly from 6 h onwards and DNA synthesis was increased from 30 h onwards. Pituitary prolactin concentration began to increase at 30 h. Significant correlations were obtained between serum prolactin and DNA synthesis from 24 to 72 h but not during the period of prolactin secretion from 6 to 24 h.

scholarly journals Perinatal Glucocorticoid Treatment Disrupts the Hypothalamo-Lactotroph Axis in Adult Female, But Not Male, Rats

Endocrinology ◽  
2006 ◽  
Vol 147 (4) ◽  
pp. 1904-1915 ◽  
Author(s):  
S. McArthur ◽  
Z.-L. Siddique ◽  
H. C. Christian ◽  
G. Capone ◽  
E. Theogaraj ◽  
...  
Keyword(s):  
Drinking Water ◽  
Sex Differences ◽  
Cell Size ◽  
Dopaminergic Neurons ◽  
Arcuate Nucleus ◽  
Male Rats ◽  
Cell Numbers ◽  
Th Cell ◽  
Prolactin Content ◽  
Pituitary Prolactin

This study aimed to test the hypothesis that the tuberoinfundibular dopaminergic neurons of the arcuate nucleus and/or the lactotroph cells of the anterior pituitary gland are key targets for the programming effects of perinatal glucocorticoids (GCs). Dexamethasone was administered noninvasively to fetal or neonatal rats via the mothers’ drinking water (1 μg/ml) on embryonic d 16–19 or neonatal d 1–7, and control animals received normal drinking water. At 68 d of age, the numbers of tyrosine hydroxylase-positive (TH+) cells in the arcuate nucleus and morphometric parameters of pituitary lactotrophs were analyzed. In control animals, striking sex differences in TH+ cell numbers, lactotroph cell size, and pituitary prolactin content were observed. Both pre- and neonatal GC treatment regimens were without effect in adult male rats, but in females, the overriding effect was to abolish the sex differences by reducing arcuate TH+ cell numbers (pre- and neonatal treatments) and reducing lactotroph cell size and pituitary prolactin content (prenatal treatment only) without changing lactotroph cell numbers. Changes in circulating prolactin levels represented a net effect of hypothalamic and pituitary alterations that exhibited independent critical windows of susceptibility to perinatal GC treatments. The dopaminergic neurons of the hypothalamic periventricular nucleus and the pituitary somatotroph populations were not significantly affected by either treatment regimen in either sex. These data show that the adult female hypothalamo-lactotroph axis is profoundly affected by perinatal exposure to GCs, which disrupts the tonic inhibitory tuberoinfundibular dopaminergic pathway and changes lactotroph morphology and prolactin levels in the pituitary and circulation. These findings provide new evidence for a long-term disruption in prolactin-dependent homeostasis in females, but not males, after inappropriate GC exposure in perinatal life.

In-vitro secretion of prolactin and growth hormone in the presence of melatonin by pituitary gland from mink kept under long or short days

1988 ◽  
Vol 119 (2) ◽  
pp. 287-292 ◽  
Author(s):  
M. Meunier ◽  
P. Brebion ◽  
N. Chêne ◽  
J.-L. Servely ◽  
L. Martinet
Keyword(s):  
Pituitary Gland ◽  
Incubation Medium ◽  
Anterior Pituitary ◽  
Prolactin Secretion ◽  
Radioreceptor Assay ◽  
History Of ◽  
Direct Target ◽  
Cervical Ganglia ◽  
Short Days

ABSTRACT Mink anterior pituitaries were incubated in Medium 199 for up to 9 or 13 days. Biological activity of prolactin and GH was determined. Daily concentrations of prolactin and GH in the incubation medium were also measured by radioimmunoassay and radioreceptor assay. When females were kept under short days for several weeks before the experiment, a significant decrease in prolactin secretion by the anterior pituitary was observed as compared with that in females maintained under long days. In contrast, secretion of GH was not modified by the photoperiodic history of the animals. Pineal gland denervation by ablation of the superior cervical ganglia a few months before the experiment, or addition of melatonin to the incubation medium of anterior pituitaries from intact or ganglionectomized females, did not modify the secretion of prolactin and GH. The pituitary gland does not therefore seem to be a direct target site for melatonin in transducing the duration of daylength on the hypothalamo-pituitary axis. J. Endocr. (1988) 119, 287–292

Release of prolactin is independent of the secretion of thyrotrophin-releasing hormone into hypophysial portal blood of sheep

1988 ◽  
Vol 117 (1) ◽  
pp. 115-122 ◽  
Author(s):  
G. B. Thomas ◽  
J. T. Cummins ◽  
B. Yao ◽  
K. Gordon ◽  
I. J. Clarke
Keyword(s):  
Reliable Method ◽  
Venous Blood ◽  
Prolactin Secretion ◽  
Portal Blood ◽  
Direct Result ◽  
Prolactin Release ◽  
Thyrotrophin Releasing Hormone ◽  
Visual Stress ◽  
Pituitary Prolactin ◽  
Hypophysial Portal

ABSTRACT In order to determine whether pituitary prolactin release was directly related to the secretion of TRH into hypophysial portal blood, serial portal and jugular venous blood samples were collected from seven lactating and three non-lactating ewes. In another experiment, samples were collected from five ovariectomized ewes while being exposed to an audio-visual stress and then later administered with chlorpromazine. Secretion of TRH was pulsatile in all ewes and independent of prolactin secretion; TRH pulses coincided with significant increases in prolactin secretion in only 15% of cases and only 29% of prolactin pulses were associated with TRH pulses. Sixty-seven per cent of suckling bouts were associated with increases in prolactin secretion, but only 22% of these were associated with significant increases in TRH secretion. Chlorpromazine increased prolactin levels fourfold but did not affect portal concentrations of TRH. Audio-visual stress was not a reliable method of causing prolactin release in this model. Mean portal concentrations of TRH and jugular concentrations of prolactin were not significantly correlated. These results show that hypothalamic TRH and pituitary prolactin are secreted independently in the sheep, implying that increases in prolactin release caused by suckling or chlorpromazine are not the direct result of increased TRH secretion. J. Endocr. (1988) 117, 115–122

Sign in / Sign up

Export Citation Format

Share Document