Modulation of luteinizing hormone receptors: effect of an inhibitor of prolactin secretion, p-coumaric acid

1983 ◽  
Vol 98 (3) ◽  
pp. 307-311 ◽  
Author(s):  
Mridula Chowdhury ◽  
S. N. Kabir ◽  
A. K. Pal ◽  
Anita Pakrashi
Keyword(s):  
Hormone Receptors ◽  
Complete Recovery ◽  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Serum Prolactin ◽  
Affinity Constant ◽  
Scatchard Analysis ◽  
Coumaric Acid ◽  
Binding Data

Daily oral administration of p-coumaric acid (PCA) at a dose of 50 mg/kg body wt for 21 days to adult male mice caused a dramatic reduction in serum prolactin concentrations. A significant fall in testicular LH binding was also observed after PCA treatment. Complete recovery of testicular LH binding was obtained by daily administration of prolactin (500 μg/mouse) when given simultaneously from day 9 of PCA treatment. A lower daily dose of prolactin (250 μg) was found to be ineffective. Scatchard analysis of binding data suggested a decrease in the number of testicular LH binding sites after PCA treatment whereas the affinity constant was unchanged. These results provide direct evidence for an inhibitory effect of PCA on prolactin secretion and also provide additional evidence in favour of a role of prolactin in the modulation of LH receptors.

scholarly journals Regulation by endogenous opioids of suckling-induced prolactin secretion in pregnant and lactating rats: role of ovarian steroids

2002 ◽  
Vol 172 (2) ◽  
pp. 255-261 ◽  
Author(s):  
M Soaje ◽  
EG de Di Nasso ◽  
RP Deis
Keyword(s):  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Endogenous Opioids ◽  
Opioid System ◽  
Serum Prolactin ◽  
Endogenous Opioid Peptides ◽  
Endogenous Opioid ◽  
Subsequent Increase ◽  
Stimulatory Action

Evidence suggests that endogenous opioid peptides are implicated in the suckling-induced prolactin rise. We explored the role of the opioid system and the participation of ovarian hormones in the regulation of prolactin induced by the suckling stimulus at the end of pregnancy in rats with developed maternal behavior, and during lactation. Suckling for 24 h induced a significant increase in serum prolactin on day 19 of pregnancy, which was increased more than three times when naloxone (2 mg/kg s.c.) or mifepristone (2 mg/kg) was administered. The combination of naloxone and mifepristone did not increase serum prolactin more than either compound alone. Administration of tamoxifen (500 microg/kg orally) on days 14 and 15 of pregnancy completely abolished the effect of naloxone, indicating a role for estrogens in establishing this inhibitory role of opioids. To examine the participation of the opioid system during lactation, we used groups of rats on days 1, 3, 5, 12 and 19 postpartum either (i) isolated from the pups for 4 h, or (ii) isolated from the pups for 3.5 h and reunited with them and suckled for 30 min. Naloxone, given just before replacing the pups, prevented the increase in serum prolactin levels observed in the suckled group of rats but had no effect on the basal levels of the isolated rats. To examine whether the participation of the opioid system in the release of prolactin is dependent on the variation of progesterone levels, rats on day 20 of pregnancy were implanted with two cannulae containing progesterone (that blocked postpartum ovulation) or cholesterol, and cesarean surgery was performed on day 21. To maintain lactation, pups (1-3 days old) were replaced every 24 h, and 4 days after the cesarean eight pups were placed in the cage at 1800 h to maintain a strong suckling stimulus during the following 24 h. Naloxone administration significantly reduced serum prolactin levels in control (cholesterol) rats but progesterone implants prevented the inhibitory effect of naloxone and this effect was not modified by treatment with estrogen. These results indicate that the opioid system modulates suckling-induced prolactin secretion, passing from an inhibitory action before delivery to a stimulatory action during lactation. This regulatory shift seems to be dependent on the fall in progesterone concentration at the end of pregnancy and the subsequent increase after the postpartum ovulation and luteal phase.

Inhibitory effect of colchicine and vinblastine on transport of glucagon receptors to the plasma membrane in cultured rat hepatocytes

1985 ◽  
Vol 106 (1) ◽  
pp. 125-131 ◽  
Author(s):  
J. Watanabe ◽  
S. Kanamura ◽  
K. Kanai ◽  
M. Asada-Kubota ◽  
M. Oka
Keyword(s):  
Plasma Membrane ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
Scatchard Analysis ◽  
Glucagon Receptor ◽  
Cultured Rat Hepatocytes ◽  
Glucagon Receptors

ABSTRACT The role of microtubules in the regulation of glucagon receptors on cultured rat hepatocytes was studied. Antimicrotubular reagents, colchicine and vinblastine, did not affect the binding of 125I-labelled glucagon to hepatocytes at 4°C. At 20 and 37 °C, however, the reagents reduced the binding after 60 or 90 min of incubation. Scatchard analysis indicated that the reduction in the binding was due to loss of glucagon-receptor populations. If hepatocytes were preincubated with both unlabelled glucagon and the reagents at 37 °C, the binding of the ligand to the cells decreased markedly after a certain delay. The reagents did not inhibit the internalization of the ligand in the cells until 30 min of incubation at 37 °C. The results suggest that the microtubule system plays a role in the transport of glucagon receptors to the plasma membrane, which is followed by their internalization. J. Endocr. (1985) 106, 125–131

Comparison of human and porcine thyroid membranes for radioreceptor assay of bovine thyrotrophin and thyrotrophin-binding inhibiting immunoglobulins

1982 ◽  
Vol 93 (3) ◽  
pp. 371-380 ◽  
Author(s):  
Hazel Humphries ◽  
Susan M. Dirmikis ◽  
D. S. Munro
Keyword(s):  
Detection Limit ◽  
Detailed Comparison ◽  
Normal Subjects ◽  
Inhibitory Effect ◽  
Radioreceptor Assay ◽  
Human Thyroid ◽  
Affinity Constant ◽  
Scatchard Analysis ◽  
Maximal Inhibition ◽  
Long Acting

A detailed comparison between the use of human and porcine thyroid membranes for the radioreceptor assay (RRA) of bovine TSH (bTSH) and thyrotrophin-binding inhibiting immunoglobulins (TBIIg) is reported. Bovine thyroid membranes were also investigated but were found to be far less satisfactory than either human or porcine thyroid membranes. The affinity constant (Ka) of the interaction of bTSH with porcine thyroid membranes (Ka = 3·3 × 109l/mol) measured by Scatchard analysis was higher than with human thyroid membranes (Ka = 2·1 × 108l/mol). Porcine thyroid membranes were more sensitive for the assay of bTSH (detection limit 30 μu., half-maximal inhibition 0·3 mu.) than human thyroid membranes (detection limit 200 μu., half-maximal inhibition 7·4 mu.). Preincubation of membranes from either species with immunoglobulin rich in long-acting thyroid stimulator (LATS) inhibited the saturable binding of 125I-labelled TSH to a greater extent than did normal immunoglobulin. The binding of 125I-labelled TSH to porcine membranes was more sensitive to the inhibitory effect of LATS-immunoglobulin and was also less affected by normal immunoglobulin than was binding to human thyroid membranes. When assayed with each type of membrane preparation there was good correlation between the RRA of immunoglobulins prepared from patients with Graves's disease and from normal subjects (n = 18) (r = 0·85, P <0·001, n = 73). The incidence of positive TBIIg in untreated Graves's disease was greater for porcine than for human thyroid membranes.

Role of the adrenal cortex in chronic stress-induced inhibition of prolactin secretion in male rats

1989 ◽  
Vol 120 (2) ◽  
pp. 269-273 ◽  
Author(s):  
A. López-Calderón ◽  
C. Ariznavarreta ◽  
M. D. Calderón ◽  
J. A. F. Tresguerres ◽  
M. I. Gonzalez-Quijano
Keyword(s):  
Adrenal Cortex ◽  
Chronic Stress ◽  
Immobilization Stress ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Prolonged Release ◽  
Plasma Prolactin

ABSTRACT The response of prolactin to chronic stress in intact, adrenalectomized and adrenomedullectomized male rats was studied. Immobilization stress in intact animals induced a significant increase in plasma concentrations of prolactin after 20 and 45 min and a significant decrease when the rats were submitted to chronic restraint (6 h daily for 4 days). Five weeks after adrenomedullectomy, plasma prolactin and corticosterone responses to chronic stress were not modified. In contrast, the inhibitory effect of chronic stress on prolactin secretion was totally suppressed by adrenalectomy. When treated with dexamethasone during the 4 days of restraint, adrenalectomized stressed rats showed similar plasma concentrations of prolactin to the intact stressed rats. These data indicate that the adrenal cortex is able to play an inhibitory role on prolactin secretion during stress only through a prolonged release of glucocorticoids. Journal of Endocrinology (1989) 120, 269–273

Endothelin receptors in human placenta: relationship to vascular resistance and thromboxane release

1990 ◽  
Vol 258 (5) ◽  
pp. E864-E870
Author(s):  
B. M. Wilkes ◽  
P. F. Mento ◽  
A. M. Hollander ◽  
M. E. Maita ◽  
S. Sung ◽  
...  
Keyword(s):  
Vascular Resistance ◽  
Human Placenta ◽  
Competitive Inhibition ◽  
Scatchard Analysis ◽  
Binding Studies ◽  
Single Class ◽  
Endothelin 1 ◽  
Binding Data ◽  
Endothelin 3

This investigation was performed to study the potential role of endothelin in the modulation of fetoplacental vascular resistance in the human placenta. Full-term placentas from uncomplicated pregnancies were studied within 30 min of delivery. The umbilical artery and vein to a single placental cotyledon were cannulated and the artery perfused with RPMI media (0.82 ml/min). Endothelin 1 caused a sustained dose-dependent increase in perfusion pressure. Infused endothelin 1 (50 nM) stimulated thromboxane release 2.3-fold compared with basal values. Thromboxane release persisted for 15 min after discontinuation of endothelin. Properties of human placental endothelin 1 receptors were defined in binding studies performed on a crude membrane fraction of placental cotyledons. Binding was saturable, reached steady state by 3 h at 25 degrees C, and was linear with protein concentration. Scatchard analysis of binding data indicated a single class of high-affinity binding sites with a Kd of 36.1 +/- 9.7 pM and a density of 185.4 +/- 9.6 fmol/mg protein (n = 5). The potency order for competitive inhibition of the binding of 125I-labeled endothelin 1 was endothelin 1 greater than endothelin 2 = endothelin 3 = sarafotoxin S6b greater than big endothelin (human) = big endothelin (porcine). Phenylephrine, bradykinin, norepinephrine, atrial natriuretic factor, diltiazem, U46619, and angiotensin II did not displace 125I-endothelin 1 from its receptors. These experiments demonstrate that endothelin 1 is a potent pressor substance in the human fetoplacental cotyledon. Pressor effects of endothelin may be mediated by a combination of direct effects and stimulation of vasoconstrictor prostanoids.

Effect of Piperoxane on Serum Prolactin: Possible Role of Epinephrine-Mediated Synapses in the Inhibition of Prolactin Secretion*

Endocrinology ◽  
1978 ◽  
Vol 102 (4) ◽  
pp. 1183-1189 ◽  
Author(s):  
M. S. GOLD ◽  
R. K. DONABEDIAN ◽  
D. E. REDMOND
Keyword(s):  
Prolactin Secretion ◽  
Serum Prolactin

Effect of modified brain histamine contents on prolactin and thyrotropin secretion in male rats

1996 ◽  
Vol 134 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Raimo K Tuominen ◽  
Leena Tuomisto ◽  
Pekka T Männistö
Keyword(s):  
Histidine Decarboxylase ◽  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Histamine Content ◽  
Male Rats ◽  
Serum Prolactin ◽  
Pituitary Hormone ◽  
Brain Histamine ◽  
Endogenous Histamine ◽  
The Brain

Tuominen RK, Tuomisto L, Männistö PT. Effect of modified brain histamine contents on prolactin and thyrotropin secretion in male rats. Eur J Endocrinol 1996;134:209–14. ISSN 0804–4643 Effects of modified brain histamine contents on thyrotropin and prolactin secretion were studied in male rats. Under basal conditions the histamine content in the hypothalamus was approximately 8–10-fold higher than that in the striatum and the rest of the brain. l-Histidine (1000 mg/kg, ip), a histamine precursor, and metoprine (20 mg/kg, ip), an inhibitor of histamine methyltransferase, elevated histamine content in the brain by 65% and 167%, respectively. When the treatments were given together an additive effect (119–250% increase) on brain histamine was observed. Metoprine significantly decreased serum prolactin levels, while l-histidine had no effect. This effect of metoprine was not modified by treatment with l-histidine. Thus, metoprine has an inhibitory effect on prolactin secretion that is not related to elevated brain histamine contents. The increased brain histamine content after l-histidine treatment had no effect on prolactin secretion. Basal levels of serum thyrotropin were decreased by both l-histidine and metoprine, l-histidine being more potent. In rats treated with α-fluoromethylhistidine, an inhibitor of l-histidine decarboxylase, the cold-induced (rats kept for 60 min at +4°C) thyrotropin secretion was increased while the stress-induced prolactin secretion was decreased. In these rats, metoprine did not affect thyrotropin release but blunted the prolactin response. In conclusion, endogenous histamine inhibits thyrotropin secretion but does not affect prolactin release. Owing to its other effects, metoprine is not suitable as a tool to elevate endogenous histamine contents in the brain, at least when the regulation of anterior pituitary hormone release is being studied. Raimo K Tuominen, Institute of Biomedicine, Department of Pharmacology and Toxicology, PO Box 8, FIN-00014 University of Helsinki, Finland

Inhibitory effect of calcium on serum prolactin

1981 ◽  
Vol 98 (3) ◽  
pp. 339-344 ◽  
Author(s):  
Klaus Kruse ◽  
Ute Kracht
Keyword(s):  
Vitamin D ◽  
Anticonvulsant Drug ◽  
Inhibitory Effect ◽  
Serum Prolactin ◽  
Drug Induced ◽  
Long Time ◽  
Nerve Tracts ◽  
Vitamin D Resistant Rickets

Abstract. The effect of calcium (Ca) infusions on serum prolactin (Prl) was studied in normal controls and children with disorders of Ca metabolism: Three patients with secondary hyperparathyroidism (vitamin D deficiency rickets), 2 children with idiopathic hypoparathyroidism, 13 epileptic patients with anticonvulsant drug induced inhibition of calcitonin (CT) secretion and 1 patient with vitamin D resistant rickets with normal CP and low PTH secretion. Ca induced a significant decline of serum Prl in most subjects which could not be explained by the associated increase of CT or decrease of iPTH. The important role of Ca for the in vitro secretion of dopamine has been established for a long time. It is speculated that the inhibitory effect of Ca infusion on serum Prl may be due to dopamine release from nerve tracts in the hypothalamus.

Quantitation of specific binding of orosomucoid to cultured microvascular endothelium: role in capillary permeability

1992 ◽  
Vol 263 (1) ◽  
pp. H48-H55 ◽  
Author(s):  
J. E. Schnitzer ◽  
E. Pinney
Keyword(s):  
Specific Binding ◽  
Endothelial Glycocalyx ◽  
Affinity Constant ◽  
Scatchard Analysis ◽  
Microvascular Endothelium ◽  
Calcium Dependent ◽  
Binding Behavior ◽  
Binding Data ◽  
Receptor Number ◽  
Apparent Equilibrium

Orosomucoid (also known as alpha 1-acid glycoprotein) is a highly sialylated, polyanionic serum glycoprotein. Its presence in vascular perfusates alters microvascular permeability, presumably by binding to the endothelial glycocalyx, but the rest of its functions remains unknown. In this study, we assess the binding of bovine serum orosomucoid (BSO) to the surface of bovine pulmonary microvascular endothelial cells (BLMVEC) in culture at 4 degrees C. The binding of radioiodinated BSO (125I-BSO) reached equilibrium after 10 min of incubation, was not calcium dependent, and was reversible by greater than 80% in 30 min. The binding of 125I-BSO was competed with unlabeled BSO but not by transferrin, immunoglobulin, gelatin, ovalbumin, mannan, fucoidan, mucin, or asialomucin. In addition, binding was not affected by the presence of galactose, glucose, fucose, mannose, N-acetyl-D-galactosamine, or N-acetyl-D-glucosamine. This binding behavior is not consistent with carbohydrate recognition by lectin-like molecules such as the asialoglycoprotein receptor. Scatchard analysis of the BSO binding to BLMVEC produced a concave-upward shaped curve, which revealed a higher affinity binding component with an apparent equilibrium affinity constant (Kd) of 8.6 nM and a maximum receptor number of 40,000/cell and revealed a moderate affinity component with a Kd of 9.1 microM with a maximum binding of 10(7) binding sites per cell. Other blood vessel-associated cells clearly bound less BSO with a lower binding affinity than the BLMVEC monolayers. From the binding data, we estimated the total increase in the negative charge of the glycocalyx with orosomucoid binding to be approximately 17 meq/l.(ABSTRACT TRUNCATED AT 250 WORDS)

PROLACTIN-LOWERING EFFECT OF LOW DOSES OF LISURIDE IN MAN

1978 ◽  
Vol 87 (2) ◽  
pp. 234-240 ◽  
Author(s):  
R. Horowski ◽  
H. Wendt ◽  
K.-J. Gräf
Keyword(s):  
Prolactin Secretion ◽  
High Serum ◽  
Serum Prolactin ◽  
Low Doses ◽  
Predominant Role ◽  
Lowering Effect ◽  
Healthy Female ◽  
Dopaminergic Mechanisms ◽  
Ergot Derivative

ABSTRACT Lisuride, a new semisynthetic ergot derivative, effectively decreased the TRH-induced hyperprolactinaemia in healthy female volunteers at a dose of 300 μg given orally. Basal prolactin levels were suppressed after a single dose of 100 and 200 μg lisuride. This effect was still present 6 h after administration. Two hundred μg lisuride also decreased the high serum prolactin levels produced by im injection of 50 mg sulpiride, and conversely, sulpiride injection abolished the prolactin lowering effect of lisuride. These results demonstrate that in man too lisuride is a very potent prolactin-lowering agent. In addition, the data support the hypothesis of a predominant role of dopaminergic mechanisms in the regulation of prolactin secretion.

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