SEARCH · PubMed Health

Results for “PROLACTIN”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMedDate not supplied

Stimulation of DNA synthesis by prolactin in human breast tumor explants. Relation to prolactin receptors.

Breast-cancer tissue from 38 patients was tested for prolactin sensitivity by measuring both 16-hour (3H)dT incorporation in tissue fragments during 24-hour organ cultures, and prolactin receptors in tumor specimens. We observed a stimulation of DNA synthesis by prolactin in 6/38 (16%) cases; the stimulation was maximum with physiological concentrations of prolactin (0.05 to 0.2 microgram/ml medium). The stimulation of DNA synthesis never occurred in the absence of prolactin receptors. There is no relation between the response to prolactin and estradiol or progesterone receptor levels, but in four cases the stimulation was observed when the three receptors were present. Finally, the response to the stimulation was independent of the clinical stage of the patient.

Breast Neoplasms↗

PubMed1991

Idiopathic prolactin cell hyperplasia of the pituitary mimicking prolactin cell adenoma: a morphological study including immunocytochemistry, electron microscopy, and in situ hybridization.

Prolactin cell adenoma is the most frequently found lesion in surgically removed pituitaries of patients with hyperprolactinemia. However, in several instances, instead of prolactin cell adenoma, other lesions are encountered by morphological investigation. We report here the morphological findings in a patient with hyperprolactinemia who underwent transsphenoidal pituitary surgery for suspected prolactin cell adenoma. A morphological diagnosis of tumor could not be confirmed and massive diffuse prolactin cell hyperplasia was identified. The aim of this publication is to describe the lesion by histology, immunocytochemistry, electron microscopy, and in situ hybridization and to call attention to primary prolactin cell hyperplasia which can mimic prolactin cell adenoma.

Diagnosis, Differential↗

PubMed1983

Studies on prolactin: conformational comparison of human, equine, and porcine pituitary prolactins.

The conformations of human, equine, and porcine pituitary prolactins, as evidenced by various optical properties, have been compared. The alpha-helix contents of all three proteins are essentially identical to each other (60 +/- 5%), as well as to prolactins isolated from other mammalian species. Direct absorption (zero and second-order), difference absorption, fluorescence emission, and circular dichroism spectra suggest that the majority of tyrosine and tryptophan side chains in these three proteins exist in very similar microenvironments within the folded forms of the hormones. Thus, the general conformational properties of these molecules are closely related to each other, and to other mammalian prolactins. Molar extinction and absorptivity values have been obtained at the absorption maximum of each species. In addition, a second molar extinction value has been determined at a particular wavelength found to be different for each, and which appears to be independent of the conformational state of the molecule. These absorptivities are useful in providing accurate prolactin concentrations in the 10(0) to 10(-2) mg/ml range. On incubation with the proteolytic enzyme thermolysin, all three hormones display an initial, short lag period during which little conformational change can be detected by difference absorption spectroscopy. For human and porcine prolactins, subsequent rates of proteolytically induced conformational collapse were found to be essentially identical. However, under similar conditions, equine prolactin loses its conformation significantly more slowly.

Animals↗

PubMed1980

Prolactin and tadpole metamorphosis. Evidence of prolactin receptors in premetamorphic Rana catesbeiana liver and tail fin.

The binding characteristics of ovine prolactin (OPRL) to a particulate fraction from liver and tail fin of Rana catesbeiana tadpoles were studied. The specific binding of [125I]oPRL to both tissues was found to be a saturable process with a single class of binding sites in each tissue. Although the dissociation constants were similar for each tissue, the tail fin demonstrated a 10-fold higher binding capacity than the liver tissue. Pretreatment of the liver and tail fin particulate fractions with degradative enzymes revealed that trypsin and phospholipase C reduced the subsequent specific [125I]oPRL binding in both tissues. However, neuraminidase treatment decreased the prolactin binding in the liver while having no effect on the tail fin. The binding of prolactin to the amphibian tissues was found to be specific for prolactin and growth hormones. [125I]oPRL binding to both tissues was a reversible process although the dissociation rate was faster for the tail fin than for the liver. Therefore, prolactin receptors are associated with both a prolactin responsive tissue, the tail, and an unresponsive tissue, the liver, in the tadpole.

Animals↗

PubMed1980

[Effect of ouabain on the lactogenic action of prolactin and on the level of mammary prolactin receptors].

Ouabain added to the culture medium of rabbit mammary gland inhibits prolactin action on the initiation of lactose and casein synthesis. The degree of inhibition is a function of the ouabain concentration in the medium. Likewise, ouabain blocks the accumulation of casein mRNA supported by prolactin. In addition, ouabain provokes a rapid disappearance of prolactin receptors. Conversely prolactin keeps its capacity to enhance the concentration of casein mRNA and the parallel casein synthesis when K+ ions are totally absent from the culture medium. These results suggest that although prolactin induces a modification of the K+/Na+ ratio in the mammary cell and ouabain prevents this effect of prolactin, the inhibitory action of ouabain on lactogenesis can be explained essentially by its effect on the hormone receptors.

Animals↗

PubMed1978

Prolactin cell adenomas of the human pituitary. Morphologic features of prolactin cells in the nontumorous portions of the anterior lobe.

Twenty pituitary glands, harbouring prolactin cell adenomas, obtained from autopsy of male and female patients of various ages and dying of different diseases have been investigated by the immunoperoxidase technique in order to reveal the morphologic changes of prolactin cells in the nontumorous protions of the anterior lobes. For comparison, 40 nontumorous pituitary glands and 20 pituitaries lodging adenomas not consisting of prolactin cells have also been studied. In all four prolactin cell adenoma cases, the anterior lobes contained numberous prolactin cells outside the tumors, indicating a lack of involution of prolactin cells in the nontumorous portions of the pituitary glands.

Adenoma↗

PubMed1991

Prolactin reduction after combined therapy for prolactin macroadenomas.

The ability of surgery or bromocriptine to produce endocrine control of a prolactin macroadenoma decreases as the prolactin level increases. Guidelines for the use of multimodality therapy have not been developed for tumors associated with markedly elevated prolactin levels. We reviewed the records of 21 patients with prolactin levels greater than 200 ng/ml treated by transsphenoidal surgery and postoperative radiotherapy with or without a dopamine agonist. Values before and after treatment were available for 19 patients (13 men and 6 women). The mean basal prolactin level before treatment for the entire group was 2410 ng/ml. Surgery and radiotherapy resulted in a 90% reduction and serum prolactin levels within normal limits in 0 of 7 patients, versus the combination of surgery, radiotherapy, and dopamine agonist, which resulted in a 99.5% reduction and values within the normal range in 12 of 12 patients. Spontaneous physiological improvement was not often observed. One woman and two men were able subsequently to have children. A plan for these patients is discussed.

Adenoma↗

PubMed1982

Prolactin-deficient variants of GH3 rat pituitary tumor cells: linked expression of prolactin and another hormonally responsive protein in GH3 cells.

GH3 cells normally synthesize and secrete two pituitary polypeptide hormones, prolactin and growth hormone. From an ethyl methane sulfonate-mutagenized population, prolactin low-producing variants have been isolated at a frequency near 20%. Intracellular prolactin synthesis in the variants was reduced 40- to 100-fold compared to wild-type cells while growth hormone synthesis varied less than 2-fold. This decrease was paralleled by a decrease in intracellular preprolactin mRNA. Although reduced, prolactin synthesis was still repressible by glucocorticoids. There was a coordinate loss of expression of p21, a thyroid and glucocorticoid hormone-regulated protein, in GH3 cells, whereas the synthesis and regulation of other hormonally responsive proteins were unimpaired in the variants. Since p21 expression was coordinately regained in a high-producing prolactin revertant cell, expression of the two proteins is tightly coupled in GH3 cells. The stability of the low-producing phenotype differed among variants. One (B2) gave rise to revertants at about 20% frequency even after two rounds of subcloning, whereas another (B3) was more stable in that only 1 weak revertant was found in 47 subclones. The reversion frequency of B3 cells was also measured at less than 0.5%. Unmutagenized GH3 cells were phenotypically stable in that no prolactin-deficient variant was found among 57 subclones. Since variants were ony found after ethyl methane sulfonate mutagenesis, the DNA alkylating agent appears to have promoted an epigenetic change in pituitary gene expression.

Alkylation↗

PubMed2004

Heparin increases prolactin and modifies the effects of fgf-2 upon prolactin accumulation in pituitary primary cultures.

We have studied the effects of heparin on prolactin accumulation in the medium from primary pituitary cultures, and whether heparin interferes with the effects of fibroblast growth factor-2 (FGF-2) on PRL regulation in vitro. In the absence of exogenous FGF-2, hepa-rin increased prolactin accumulation in the culture medium in a dose-dependent manner. FGF-2 also increased the prolactin levels of primary cells in a time- and dose-dependent manner. However, low doses of heparin reduced the effects of FGF-2, but higher doses of heparin increased the maximal FGF-2-induced prolactin secretion and ED50. In vivo estrogenization of rats resulted in the abolition of FGF-2 capability to promote prolactin release in vitro. However, heparin restored cell responsiveness to FGF-2. Our results suggest that heparin, when present in the medium, binds FGF-2, therefore reducing its ability to interact with FGF receptors in a dose-dependent manner up to a critical molar concentration, at which heparin itself starts to activate the FGF receptor, and strengthens the activation induced by its proper ligand, FGF-2. Prolactin responses to FGF-2 are blocked by estrogen pretreatment, and it is probable that this introduces lactotroph cells in the proliferative stage. In conclusion, heparin modulates PRL secretion and PRL responses to FGF-2 in vitro.

Animals↗

PubMed1980

Effects of season, lactation and plane of nutrition on prolactin concentrations in ovine plasma and the role of prolactin in the control of ewe fertility.

Plasma prolactin concentrations during the first 2 months after lambing, at oestrus, and during early pregnancy were investigated in 2 experiments in which Finn x Dorset Horn ewes were mated at an induced oestrus approximately 9 weeks after lambing. Mean prolactin concentrations between lambing and mating were dependent on seasons, being greater than 260 ng/ml plasma in lactating ewes mated in July and less than 150 ng/ml in those mated in October. Within 8 days of weaning of the lambs at 50 days post partum values declined to 122 and 30 ng/ml respectively. Plane of nutrition had little effect on prolactin levels. Higher prolactin values were recorded during oestrus in ewes mated in March or July, the normal period of anoestrus, than in December, the normal breeding season, mean values being approximately 200 ng/ml and 35 ng/ml respectively. The mean increases in the concentrations of prolactin during oestrus were smaller in lactating than non-lactating ewes. It is suggested that these differences in prolactin levels may be responsible for the effects of season and lactation on ewe fertility.

Animal Nutritional Physiological Phenomena↗

PubMed1988

Increased prolactin response to TRH in polycystic ovary syndrome with low basal prolactin values.

An intravenous TRH loading test with 200 micrograms TRH was carried out in 9 hypoprolactinemic (serum prolactin less than 100 mIU/ml) and 6 normoprolactinemic PCO patients and 6 normal subjects. Basal and stimulated prolactin and TSH levels were measured. The latter were within normal values. Prolactin responses to TRH were exaggerated in PCO patients, irrespective of the basal prolactin values. According to literary data, these results indicate that increased prolactin response to TRH in PCO is independent of the basal prolactin values and suggest disturbed tuberoinfundibular dopaminergic function.

Adolescent↗

PubMed1990

Expression of new members of the prolactin growth hormone gene family in bovine placenta. Isolation and characterization of two prolactin-like cDNA clones.

Two prolactin-like proteins (bPLP-I and bPLP-II) were deduced from the nucleotide sequence analyses of the cDNA clones derived from a bovine (Bos taurus) term placenta. These proteins resembled bovine prolactin but were different from the reported bovine placental lactogens or prolactin-related proteins. The predicted amino acid sequences of these clones showed 45-51% identity with bovine prolactin and 23-24% with bovine growth hormone. The two new clones show 62 and 39% overall homology with each other at the levels of nucleotide and amino acid sequences, respectively. bPLP-I, bPLP-II, placental lactogens, prolactins (PRLs), and other prolactin-like proteins isolated from cow, mouse, and rat share 7 common amino acid residues. Five of the 7 residues are conserved by other members of the family such as growth hormones, suggesting that they may be essential for the common structural features of the gene family. The other 2 residues are uniquely conserved in bovine, mouse, and rat placental lactogens, PRLs, and PRL-like proteins, predicting their indispensable roles in binding to the specific receptors. bPLP-I and bPLP-II, as well as bPLP-III, are shown to be expressed stage specifically and predominantly in full-term bovine placentas.

Amino Acid Sequence↗

PubMed1984

Characterization of antisera to a partially purified prolactin receptor: effect on prolactin binding in different target tissues.

Prolactin (PRL) receptors have been purified by affinity chromatography using a lactogenic hormone (human growth hormone, hGH) coupled to Affigel-10. The mean binding capacity of 3 separate purifications was 1.18 +/- 0.26 nmoles prolactin per mg protein, representing a 836-fold purification over crude microsomes and 4000-5000-fold over mammary gland homogenates and 16% purity. The receptor was characterized by HPLC using a TSK-SW-4000 and 3000 column connected in series and eluted in 0.1 M borate buffer containing 0.2 M NaCl and 0.1% Triton. A single peak of [125I]hGH binding activity with a retention time of 45.2 min (22.6 ml), representing an apparent molecular weight of 133000, was observed. A single peak of activity was also observed following polyacrylamide gel electrophoresis of the purified receptor in 0.1% Triton coincident with the Coomassie-stained protein band. Antibodies to the partially purified receptor preparations were prepared in sheep, goats and guinea pigs. Antisera to the prolactin receptor prepared in all three species were capable of inhibiting the binding of 125I-labeled ovine prolactin to receptors from rabbit mammary glands. Significant inhibition of binding was observed at antisera dilution of 1:10 000 with the sheep antiserum being the most potent (half-maximal inhibition (IM50) = 1:5700). All three antisera were able to inhibit PRL binding completely, but failed to affect labeled insulin or hCG binding and had very little effect on bGH binding. The specificity of the sheep antiserum was tested in rabbit mammary glands, ovary, adrenal, pig mammary glands and 8 rat tissues which contain PRL receptors. The antiserum was able to inhibit the binding of labeled PRL in all tissues, with the inhibition curves for the rat tissues being non-parallel when compared to rabbit mammary gland, suggesting a homology but not a complete identity between PRl receptors in various tissues and animal species. These studies demonstrate that prolactin receptors can be purified from rabbit mammary tissue and that antisera can be produced in several species. In addition, the binding studies suggest that in the various tissues the receptor molecule is more or less exposed to interaction with the antisera, or that the receptor protein differs somewhat between species.

Animals↗

PubMed1991

Comparison of long and short forms of the prolactin receptor on prolactin-induced milk protein gene transcription.

The biological activities of long and short forms of the prolactin receptor have been compared. These two receptors expressed in mammalian cells were shown to bind prolactin with equal high affinity. The ability of these different forms to transduce the hormonal message was estimated by their capacity to stimulate transcription by using the promoter of a milk protein gene fused to the chloramphenicol acetyltransferase (CAT) coding sequence. Experiments were performed in serum-free conditions to avoid the effect of lactogenic factors present in serum. An approximately 17-fold induction of CAT activity was obtained in the presence of prolactin when the long form of the prolactin receptor was expressed, whereas no induction was observed when the short form was expressed. The present results clearly establish that only the long form of the prolactin receptor is involved in milk protein gene transcription.

Animals↗

PubMed1982

Characterization of [125I]-iodo-ovine prolactin and evaluation of prolactin receptor assay methods.

In an attempt to establish more rigorous conditions for assay of prolactin receptor, a study of the preparation, recovery and specific binding of iodoprolactin was conducted. Averaging the results of 20 preparations starting with 5 micrograms prolactin preparation and iodinated by a lactoperoxidase method, an average of 0.62 +/- 0.12 micrograms of the iodinated prolactin was recovered in a form capable of binding to excess rat liver membrane preparations, corresponding to between 24 and 51% of the total recovered iodinated prolactin. Based on preliminary amino acid analysis and N-terminus determination, 53% of a weighed amount of ovine prolactin was determined to be protein with the N-terminal amino acid being consistent with homogeneity. The percent specific binding assay (single point assay) and Scatchard analysis were tested for their ability to give assay results in a direct relationship to sample receptor. Scatchard analyses were determined to be a superior method to the percent specific binding assay. Using commonly employed conditions for the percent specific binding assay, the relative amounts of receptor found in increasing amounts of sample were significantly less than that found by Scatchard analysis in all likelihood due to the use of subsaturating concentrations of iodohormone. As more hormone was added per assay tube, the relationship of sample receptor to the results of the single point assay improved, but the results never equaled those of Scatchard analyses. Thus, many workers who have used the percent specific binding assay under nonsaturating conditions have underestimated the relative receptor contents of samples.

Animals↗

PubMed2005

Action of prolactin, prolactin-releasing peptide and orexins on hypothalamic neurons of adult, early postnatally overfed rats.

OBJECTIVES: Hypothalamic neurons of rats overweight due to early postnatal overfeeding (SL) differ from those of control rats in their responses to feeding relevant hormones like leptin or insulin. The question arose whether prolactin and prolactin-releasing peptide (PrRP) express also differential action in SL rats. These peptides are described to have an effect on food intake and body weight regulation. Prolactin is co-synthesized in lateral hypothalamic neurons together with orexins that were also analyzed in this study. METHODS: Single unit activity was extracellularly recorded in brain slices from adult control rats (CL) and from rats previously raised in small litters (SL). The action of the peptides on the firing rates was evaluated in the medial parvicellular part of the paraventricular nucleus (PaMP) and the medial arcuate nucleus (ArcM). RESULTS: In control rats, PrRP significantly activated PaMP neurons, whereas prolactin and orexin-A induced also inhibition. In SL rats, there was a significantly different effect of orexin-B on PaMP neurons: the main effect changed from activation in controls to inhibition. ArcM neurons of both control and SL rats were mainly excited by prolactin and orexins. CONCLUSION: Changes acquired during early development of neuronal responses to feeding relevant peptides are not a general non-specific mechanism of neurochemical plasticity, but concern specific hypothalamic nuclei and/ or hormones and neuropeptides. The increase in inhibition by orexin-B of hypothalamic paraventricular neurons could in vivo contribute to the neonatally acquired disposition towards persistingly increased food intake and reduced energy expenditure of overweight SL rats.

Animals↗

PubMed1994

Circulating prolactin and tumoral prolactin receptors in men with tongue cancer: a preliminary study.

Pre-therapeutic circulating prolactin levels and tumoral prolactin receptors (PRLR) were determined in 25 male patients with tongue cancer. The patients were divided into PRLR positive (PRLR+) and PRLR negative (PRLR-) groups. The overall survival was statistically non-significant between these two groups of PRLR as well as when considering 2% as the cut-off level. Moreover, no correlation was observed between PRLR status and clinicopathologic prognosticators. Furthermore, patients with < 2% PRLR had significantly higher levels of circulating prolactin than their counterparts (P < 0.05). Patients with PRLR- tumors having hyperprolactinemia (prolactin > 15.0 ng/ml) had unfavourable overall survival (chi 2 = 4.08, df = 1, P < 0.04) than those with normoprolactin (prolactin < 15.0 ng/ml). From this pilot study, it seems that PRLR negativity with hyperprolactinemia could be used as an independent predictor of short-term prognosis in cancer tongue patients.

Carcinoma, Squamous Cell↗

PubMed1987

Hemodynamics, prolactin and catecholamine levels during hemorrhagic shock in dogs pretreated with a prolactin inhibitor (bromocriptine).

Bromocriptin, a dopaminomimetic drug, causing inhibition of prolactin secretion, was used in experiments on haemorrhagic shock in dogs. 5 dogs were treated with bromocriptine (0.4 mg.day-1) for two days; a further 5 dogs were used as control animals. 30% of the blood volume was drawn from each dog. Mean arterial blood pressure, heart rate, central venous pressure, acid-base status, prolactin, GH and catecholamine levels were checked before blood letting and monitored until 1 hour after blood letting. Animals treated with bromocriptine showed a significant decrease of the mean arterial blood pressure and of the prolactin rate and a significant increase of catecholamine levels. Control animals, instead, showed a significant increase of the prolactine and catecholamine rates. The results obtained suggest that bromocriptine can constitute an additional hypotensive factor in subjects with acute haemorrhage. A considerable amount of research work previously carried out has shown a close correlation between stress and hyper-prolactinemia. The increase of prolactinemia and the effects of bromocriptine on this hormone during surgical stress is particularly interesting due to its possible implications (Lanza V. et coll., 1983). In previous experiments involving animals it was found that Prolactin exerts positive chronotropic and hypertensive effects (Horrobin D.F., 1977) whilst bromocriptine is a potent agonist of D2 dopaminergic receptors (Thorner M.O. et coll., 1980). Dopamine was found to be particularly useful in the clinical treatment of shock thus suggesting an involvement of peripheral D2 receptors. On the basis of these observations we have considered it worthwhile to investigate the haemodynamic effects of bromocriptine in haemorrhagic shock.

Animals↗