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.

Effects of domperidone on the secretion of prolactin from rat anterior pituitary glands

1982 ◽  
Vol 94 (3) ◽  
pp. 317-326 ◽  
Author(s):  
A. M. Bentley ◽  
M. Wallis
Keyword(s):  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Constant Rate ◽  
Pituitary Glands ◽  
Prolactin Content ◽  
Tissue Incorporation ◽  
Perifusion System

The effects of domperidone on prolactin secretion from the anterior pituitary glands of female rats were studied. A perifusion system and radioimmunoassay were used to study secretion; static incubations and incorporation of [3H]leucine were used to measure biosynthesis. During perifusion, intact anterior lobes showed a constant rate of prolactin secretion for up to 5 h (after a 90-min preincubation to stabilize the tissue). Incorporation studies revealed an increase in protein synthesis in perifused hemipituitary glands. When glands were treated with 10 nm-domperidone, prolactin secretion began to decline after the first hour, reaching a maximum of 40–50% inhibition after a further 90 min. Growth hormone secretion showed no such decline. Inhibition of prolactin secretion continued for up to 2 h after withdrawal of the drug. Treatment with 100 nm-dopamine resulted in a more rapid inhibition of secretion, but the effect was reversed on withdrawal of the catecholamine. The prolactin content of perifused hemipituitary glands was measured after treatment with domperidone; the contents of control and treated glands did not differ, but were depleted compared with hemipituitary glands which had not been perifused.

Serotonin induces gonadotrophin release through stimulation of LH-releasing hormone release from the median eminence

1986 ◽  
Vol 111 (2) ◽  
pp. 309-315 ◽  
Author(s):  
M. L. Vitale ◽  
M. N. Parisi ◽  
S. R. Chiocchio ◽  
J. H. Tramezzani
Keyword(s):  
Median Eminence ◽  
Anterior Pituitary ◽  
Female Rats ◽  
Male Rats ◽  
Tissue Samples ◽  
Releasing Hormone ◽  
The Third ◽  
Lh Releasing Hormone ◽  
Perifusion System

ABSTRACT The effects of serotonin (5-HT) on the release of gonadotrophins and LH-releasing hormone (LHRH) were examined in an in-vitro perifusion system using median eminences and/or anterior pituitaries obtained from male or pro-oestrous female rats. Animals were killed by decapitation between 12.00 and 13.00 h. A serial double-chamber perifusion system was employed. Three types of experiments were performed. In the first, median eminences were placed in the first chamber and one anterior pituitary in the second chamber. In the second group, only the anterior pituitary was perifused. In the third group, only five median eminences were perifused. In the first and second experiments, LH, FSH and prolactin were determined in the perifusion efflux by radioimmunoassay (RIA). In the third experiment, LHRH was determined by RIA. Addition of 5-HT (final concentrations 0·06, 0·6 and 6·0μmol/l) into the first chamber containing the median eminences stimulated the release of LH and FSH from the pituitary, but did not affect the levels of prolactin in the effluent in the same experiment (prooestrous rats). The stimulatory effect of 5-HT was blocked by the addition of cyproheptadine (1 μmol/l) in the perifusion fluid. The introduction of 5-HT (0·6 μmol/l) into the tube connecting the first and second chambers did not modify the release of LH, nor did 5-HT added to the pituitaries perifused alone. Injection of 5-HT into the first chamber (median eminences), containing tissue samples from male rats, stimulated LH release, but to a significantly (P< 0·001) lower degree than that found when samples from pro-oestrous females were used (P< 0·0001). When median eminences from pro-oestrous rats were perifused alone, injection of 5-HT produced an immediate release of LHRH which peaked during the first 10 min of collection and lasted for 30 min; in these experiments, a clear relationship existed between dose of 5-HT and release of LHRH (P<0·02). The stimulatory effect of 5-HT was blocked by the addition of cyproheptadine (5 μmol/l) or methiothepin (5 μmol/l). These results demonstrate that 5-HT stimulates gonadotrophin release by acting directly on LHRH terminals in the median eminence from pro-oestrous rats. Furthermore, the effect of 5-HT on LHRH release was dose dependent and was nullified by 5-HT receptor blockers (cyproheptadine and methiothepin). J. Endocr. (1986) 111, 309–315

Size heterogeneity of prolactin secreted from and stored in the rat anterior pituitary gland in vitro

1984 ◽  
Vol 4 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Andrew M. Bentley ◽  
Teresa K. Surowy ◽  
Michael Wallis
Keyword(s):  
Anterior Pituitary ◽  
Relative Proportion ◽  
Gel Filtration ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Glands ◽  
Dimeric Form ◽  
Size Heterogeneity ◽  
Pituitary Prolactin

The size heterogeneity of rat pituitary prolactin was investigated using anterior pituitary glands from female rats incubated in vitro and gel filtration on Sephadex G-100. Monomeric prolactin was preferentially secreted compared with dimeric and ‘trimeric” material. When glands were incubated with dopamine, prolactin secretion was inhibited and the relative proportion of dimer in the gland (but not the medium) was decreased. Morphine sulphate reversed the effect of dopamine on prolactin secretion and on the proportion of prolactin in the gland that was in the dimeric form. The results suggest that monomeric prolactin is more readily secreted than dimer, and that dopamine decreases the production or stability of the dimer.

A COMPARISON OF THE EFFECTS OF FOUR ERGOT DERIVATIVES ON PROLACTIN SECRETION BY DISPERSED RAT PITUITARY CELLS

1980 ◽  
Vol 87 (1) ◽  
pp. 95-103 ◽  
Author(s):  
G. DELITALA ◽  
T. YEO ◽  
ASHLEY GROSSMAN ◽  
N. R. HATHWAY ◽  
G. M. BESSER
Keyword(s):  
Anterior Pituitary ◽  
Ergot Alkaloids ◽  
Prolactin Secretion ◽  
Pituitary Cells ◽  
Inhibitory Effects ◽  
Prolactin Release ◽  
Ergot Derivatives ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

The inhibitory effects of dopamine and various ergot alkaloids on prolactin secretion were studied using continuously perfused columns of dispersed rat anterior pituitary cells. Bromocriptine (5 nmol/l) and lisuride hydrogen maleate (5 nmol/l) both inhibited prolactin secretion, the effects persisting for more than 3 h after the end of the administration of the drugs. A similar although less long-lasting effect was observed with lergotrile (50 nmol/l) and the new ergoline derivative, pergolide (5 nmol/l). These effects contrasted with the rapid disappearance of the action of dopamine. The potency estimates of the ergots relative to that of dopamine were: lergotrile, 2·3; bromocriptine, 13; lisuride, 15; pergolide, 23. The dopamine-receptor blocking drugs, metoclopramide and haloperidol, antagonized the prolactin release-inhibiting activity of the compounds; bromocriptine and lisuride showed the highest resistance to this dopaminergic blockade. The results suggested that the direct effect of the ergot derivatives on dispersed pituitary cells was mediated through dopamine receptors and emphasized the long-lasting action of bromocriptine and lisuride in vitro.

scholarly journals Direct Stimulatory Effects of Oxytocin in Female Rat Gonadotrophs and Somatotrophs In Vitro: Comparison With Lactotrophs

Endocrinology ◽  
2014 ◽  
Vol 156 (2) ◽  
pp. 600-612 ◽  
Author(s):  
Arturo E. Gonzalez-Iglesias ◽  
Patrick A. Fletcher ◽  
José A. Arias-Cristancho ◽  
Ruth Cristancho-Gordo ◽  
Cleyde V. Helena ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Cell Types ◽  
Pituitary Hormones ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Cells ◽  
Female Rat ◽  
Dependent Manner ◽  
Rat Pituitary Cells

The peptide oxytocin (OT) is secreted by hypothalamic neurons and exerts numerous actions related to reproduction. OT stimulation of prolactin secretion in female rats is important during the estrous cycle, pregnancy, and lactation. Here we report that OT also stimulates transients of intracellular Ca2+ concentration in somatotrophs and gonadotrophs as well as the release of GH and LH in a dose-dependent manner with EC50 values that closely correspond to the ligand affinity of the OT receptor (OTR). Remarkably, the hormone-releasing effect of OT in these two cell types is 2 orders of magnitude more sensitive than that in lactotrophs. The specific OTR agonist [Thr4,Gly7]-oxytocin acutely stimulated the release of LH, GH, and prolactin from female rat pituitary cells in primary culture and increased intracellular Ca2+ concentration in gonadotrophs, somatotrophs, and lactotrophs. In these three cell types, the effects on hormone release and intracellular Ca2+ of both OT and [Thr4,Gly7]oxytocin were abolished by the specific OT receptor antagonist desGly-NH2-d(CH2)5[D-Tyr2,Thr4]OVT but not by the highly selective vasopressin V1a receptor antagonist, d(CH2)5[Tyr(Me)2,Dab5]AVP. Furthermore, 10 nM arginine vasopressin stimulated LH and GH release comparably with a dose of OT that was at least 10 times lower. Finally, the presence of the OTR-like immunoreactivity could be observed in all three cell types. Taken together, these results show that OT directly stimulates gonadotrophs, somatotrophs, and lactotrophs through OT receptors and suggest that OT signaling may serve to coordinate the release of different pituitary hormones during specific physiological conditions.

Inhibitory effects of fumagillin and its analogue TNP-470 on the function, morphology and angiogenesis of an oestrogen-induced prolactinoma in Fischer 344 rats

1996 ◽  
Vol 150 (1) ◽  
pp. 99-106 ◽  
Author(s):  
H Stępień ◽  
M Grochal ◽  
K W Zieliński ◽  
S Mucha ◽  
J Kunert-Radek ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Anterior Pituitary ◽  
Angiogenesis Inhibitors ◽  
Prolactin Secretion ◽  
Prolonged Treatment ◽  
Endothelial Cell Proliferation ◽  
Pituitary Cells ◽  
Fischer 344 ◽  
F344 Rats

Abstract The process of angiogenesis occurs in many physiological states, but it is also essential for the growth of solid tumours and metastasis formation. An abnormal arterial vascularization has been shown in prolactin-secreting pituitary adenomas induced by prolonged treatment with oestrogens in Fischer 344 (F344) rats. It is thought that anti-angiogenic agents might be useful in therapy for these tumours. Fumagillin and its analogue TNP-470 are known to inhibit endothelial cell proliferation selectively, but their effect on lactotroph cell secretory function and prolactinoma formation has not yet been described. The aim of the present study was to examine the effects of fumagillin and TNP-470 on prolactin secretion, and morphological and vascular changes within the anterior pituitary in long-term oestrogen-treated male F344 rats in vivo and in vitro. As expected, 7 weeks after s.c. implantation of Silastic tubes containing 10 mg diethylstilboestrol (DES), a very high rise in serum prolactin levels was found. Both angiogenesis inhibitors injected s.c. at doses of 10 mg/kg body weight for 24 days attenuated the stimulatory effect of DES on prolactin production and release. They also diminished prolactin cell density and inhibited cell proliferation expressed as the number of anterior pituitary cells labelled with bromodeoxyuridine (BrdU), but the effect of TNP-470 was minor compared with fumagillin. Both angioinhibitors suppressed neovascularization within the anterior pituitary with similar potency but, on the other hand, they did not affect DES-induced increases in prolactin secretion from cultured rat pituitary cells and cell proliferation in vitro. In conclusion, our results provide strong evidence for the anti-tumour and anti-prolactin activity of angiogenesis inhibitors in the experimentally oestrogen-induced pituitary adenoma; this might be mediated indirectly through the inhibition of angiogenesis. Journal of Endocrinology (1996) 150, 99–106

Differential effects of forskolin on LH and GH release

1985 ◽  
Vol 249 (4) ◽  
pp. E392-E397
Author(s):  
W. S. Evans ◽  
T. H. Brannagan ◽  
E. R. Limber ◽  
M. J. Cronin ◽  
A. D. Rogol ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Gonadotropin Releasing Hormone ◽  
Female Rats ◽  
Second Phase ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Lh Release ◽  
Biphasic Release

The effects of forskolin, an agent which increases intracellular levels of cAMP, on basal luteinizing hormone (LH) and growth hormone (GH) release and on gonadotropin-releasing hormone (GnRH)-stimulated LH release were documented. Continuously perifused dispersed anterior pituitary cells from female rats at random stages of the estrous cycle were used. Secretory rates of both LH and GH increased in a concentration-dependent manner in response to a 1-h challenge with 0.03, 0.1, 0.3, 1, or 3 microM forskolin. In response to 0.3 microM forskolin, maximum GH release was achieved within 15-20 min, after which secretion decreased. In contrast, LH release increased gradually, became maximal at 1.5-2 h, and remained constant until the forskolin was withdrawn. Cells exposed to 10 nM GnRH for 4 h exhibited a biphasic release of LH with the interphase nadir occurring at 30 min. The second phase of LH release was enhanced by simultaneous addition of forskolin with the GnRH. Whereas second phase release did not increase further, exposure of the cells to forskolin for 60 or 120 min before GnRH resulted in increased first-phase LH release. We suggest that, whereas our data are consistent with a role for cAMP in mediating the acute release of GH, cAMP may be involved in the process through which nonimmediately releasable LH becomes available for release.

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