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PubMed2004

Importance of serum prolactin determination in metastatic breast cancer patients.

AIM: To correlate prolactin concentrations in the sera of patients with metastatic breast cancer with time interval to appearance of metastases, their location, and size. METHOD: The prospective study included 46 female patients with histologically confirmed diagnosis of breast cancer. The patients were recruited from the Health Center outpatient clinic and University Hospital Center day-care hospital in Banja Luka, Bosnia and Herzegovina, from January to August 1988. The follow up lasted 5 years. Serum concentrations of prolactin were measured in all patients before (baseline levels) and after the therapy at regular time intervals during the observation period. Their prolactin concentrations were compared with prolactin concentrations in 40 healthy women and 33 female patients with other types of cancer, who served as control groups. Time interval to metastases development, their size, and location were determined in breast cancer patients and compared with those in patients with other types of cancer. RESULTS: The baseline serum concentrations of prolactin were higher in breast cancer patients than in healthy women (610 vs 442 mU/L; p=0.04; Mann-Whitney test), and in patients with other locations of cancers (662 vs 481 mU/L, respectively; p=0.02; Mann Whitney test). Metastases developed in all hyperprolactinemic patients, whereas a third of normoprolactinemic were free of metastases. The average time interval before the occurrence of metastases in patients with very high serum concentrations of prolactin was significantly shorter than that in patients with very low prolactin concentrations (54.3 vs 6.1 months; p<0.001; Mann Whitney test). In hyperprolactinemic patients with metastatic breast cancer, there was a significant correlation between the serum concentration of prolactin before treatment and the time to metastases (r= -0,47; p=0.03) and the size of metastases (r=0,64; p=0.001). CONCLUSION: Hyperprolactinemia could be an indicator of disease progression and poor prognosis in patients with metastatic breast cancer.

Adult↗
PubMed2004

Serum prolactin in human immunodeficiency virus infection.

Patients infected with human immunodeficiency virus (HIV) have higher serum prolactin compared to healthy controls but this is controversial. As part of a laboratory audit investigating the interference of macroprolactin in our prolactin assay, we investigated whether low biological activity macroprolactin could account for the increased serum prolactin concentrations observed in HIV infection. We, therefore, compared serum total prolactin and free prolactin in 32 subjects infected with HIV (HIV+ve) with 52 subjects not infected with HIV (HIV-ve). Serum total prolactin concentrations were similar in HIV+ve and HIV-ve patients [median (95% confidence limits); 167.0 (122.4 - 313.8) vs 206.5 (187.8 - 248.4) mU/L respectively]. Serum free prolactin concentrations were lower (p <0.005) in HIV+ve subjects than in HIV-ve subjects [112.0 (91.1-141.8) vs 171.0 (154.5 - 200.9) mU/L respectively; p<0.0005]. These results are consistent with the notion that low biological activity macroprolactin contributes to circulating prolactin concentrations in HIV+ve subjects.

Adult↗
PubMedDate not supplied

[Effects of guanine nucleotides and protein kinase C on prolactin-stimulated release of Ca from intracellular stores of pig oocytes].

The effects of guanine nucleotides and protein kinase C on prolactin-stimulated Ca2+ release from intracellular stores of pig oocytes were studied using the fluorescent dye chlorotetracycline. The effect of prolactin was related to the protein kinase C activation. Inhibition of protein kinase C stimulated Ca2+ release from intracellular stores of the pig oocytes treated with 5 ng/ml prolactin in the presence of extracellular Ca2+ and inhibited Ca2+ release from intracellular stores of the pig oocytes treated with 50 ng/ml prolactin. In a Ca2+-free medium, prolactin did not stimulate Ca2+ release from intracellular stores of the oocytes treated with GDP in the presence of GDP. GTP inhibition of protein kinase C activated Ca2+ release from intracellular stores of the pig oocytes treated with 5 ng/ml prolactin and inhibited Ca2+ release from intracellular stores of the pig oocytes treated with 50 ng/ml prolactin. These data suggest the influence of guanine nucleotides and protein kinase C on calcium metabolism, stimulated by prolactin.

Animals↗
PubMedDate not supplied

[Correlation between levels of prolactin in maternal serum, fetal serum and amniotic fluid in childbirth at term].

In 117 parturients with 38-41 gestation weeks, prolactin was analysed by the radioimmunologic method in the mother serum, the umbilical cord serum and vein, and in the amnionic fluid. Three groups of parturients and their newborns were examined: the group (n = 44) with the birth having started spontaneously with the appearance of labour pains 1/10 minutes, the group (n = 38) with a programmed birth induced by the infusion of oxytocin, and the group (n = 35) with the birth comprising elective cesarean section. The concentration of prolactin in the examined sera is characterized by considerable individual oscillations. The highest prolactin level was in the amnionic fluid (395.6 +/- 130.1 mu/L) and the lowest in the mother serum (174.6 +/- 84.1 mu/L) which shows a statistically significant difference (p less than 0.01). Prolactin values in the umbilical artery (244.6 +/- 98.3 mu/L) and vein (230.4 +/- 91.7 mu/L) are significantly (p less than 0.001) higher than the value in the mother sera and significantly lower (p less than 0.001) than the prolactin concentration in the amnionic fluid. The difference of the prolactin values in the sera of the umbilical cord blood vessels has no statistical significance (p greater than 0.05). Nor is there any statistically significant difference between prolactin concentrations in spontaneous and induced deliveries versus those in deliveries terminated with elective cesarean section (p greater than 0.05). A correlation analysis of the functional connection of prolactin in the sera of the mother, fetus, and amnionic fluid gives the correlation coefficient values of high statistical significance (0.482 less than r less than 0.906; p less than 0.001).

Amniotic Fluid↗
PubMed1991

Effect of a melatonin implant on the circadian variation of plasma prolactin and rectal temperature in newborn sheep.

Plasma prolactin and rectal temperature show a circadian rhythm in newborn sheep raised under continuous light. Melatonin lowers the concentration of plasma prolactin but it is not known if it affects its circadian rhythm. To detect whether melatonin acts on the circadian system we studied the effect of a subcutaneous melatonin implant in the circadian rhythms of prolactin and rectal temperature in newborn lambs raised under continuous light. We placed catheters in the pedal artery and vein in 9 newborn lambs (2-5 days of age). A subcutaneous melatonin implant was placed in 4 of the lambs at 9-12 days of age. Blood samples and rectal temperature measurements were obtained hourly for a period of 24 h, 11-15 days after the implant, at 20-27 days of age. To avoid interferences of heparin in our melatonin assay, serum melatonin concentration was measured before and during the implant in three additional newborns. Prolactin and melatonin were measured by RIA. Melatonin concentrations were 52.8 +/- 45.9 pg/ml (day) and 315.5 +/- 77.0 pg/ml (night) before treatment (SEM, P less than 0.001), and increased to 594.1 +/- 54.5 pg/ml after placing the implant (there was no difference in melatonin concentration between day and night during the time that the implant was in place). Melatonin had no effect on rectal temperature or its rhythm, but decreased basal plasma prolactin concentration (control: 97.5 +/- 11.3 ng/ml; treated: 25.1 +/- 2.4 ng/ml, P less than 0.001) and abolished the prolactin circadian rhythm, (Cosinor analysis): control: log prolactin (ng/ml) = 1.8 + 0.26 cos 15 (t - 11.16), p = 0.05; treated: log prolactin (ng/ml) = 1.2 + 0.14 cos 15 (t - 9.43), P = 0.36.

Animals↗
PubMed1977

Prolactin and murine mammary tumorigenesis: a review.

It is unequivocal that prolactin is an influential hormone in murine mammary tumorigenesis. The Berenblum hypothesis (7), a well-known theoretical model of tumorigenesis that depicts this oncogenic process as a two-step mechanism, i.e., initiation and promotion, is a conceptual scheme in which the action of prolactin in mammary tumorigenesis may be understood. According to this conceptual model, prolactin would participate in both the initiation and promotion steps of mammary tumorigenesis, In the initiation phase, variations in prolactin secretion appear to influence the metabolism of the mammary epithelium, so that the epithelium would be either more receptive to or refractory to an initiating agent (e.g., chemical carcinogen, physical carcinogens, oncogenic viruses, ets.) i.e., a permissive action. In the promotion phase, prolactin may act as either a promoter or an antipromoter of the "transformed" mammary epithelium. In promotion, the hormone may either directly or indirectly (via the ovary) stimulate mitotic activity of the "transformed" epithelium. In antipromotion the hormone, in the presence of requisite hormones (e.g., glucocorticoids), may synergistically induce differentiation (e.g., lactation) in the "transformed" epithelium. A tumor would result in the former (promotion) but not in the latter (antipromotion) case. Whether or not prolactin is significantly influential in human breast tumorigenesis remains to be determined. This is an extremely important area of research which is justifiably receiving increased attention. For if prolactin can be shown to influence human breast epithelium in a manner similar to its effect on rodent mammary tissue, then prophylactic and/of chemotherapeutic control of human breast tumorigenesis may be feasible by appropriate drug-mediated prolactin suppression.

Adrenal Glands↗
PubMed1991

Temperature dependence of prolactin endocytosis and casein exocytosis in epithelial mammary cells.

As previously reported in epithelial mammary cells of lactating rabbit, prolactin exerts a stimulatory effect on casein secretion. After binding to a membrane receptor, the complex hormone-receptor is internalized in mammary cells. Peptide hormone action involves the generation of second messengers. These second messengers can be emitted as soon as hormone is linked to the membrane receptor. However, it is not excluded that endocytosis and transfer of prolactin inside the cell take part in the emission of second messenger and related secretory response. In order to precise intracellular transport pathways in the lactating mammary cell, we have examined the effects of reduced temperature on the one hand on prolactin endocytosis, on the other hand on casein secretion and on the stimulating effect of prolactin on casein secretion. Endocytosed prolactin was cytochemically localized mainly on the plasma membrane at 4 degrees C. At 25 degrees C, the hormone accumulated, during 60 min, in endosomes and multivesicular bodies. At 37 degrees C, prolactin was detectable after 15 and 30 min inside the cells and disappeared after 60 min. Transport and exocytosis of secretory proteins were only partly inhibited at 25 degrees C as attested by autoradiography localization and biochemical assays of newly synthesized caseins. However, at 25 degrees C, prolactin was no more able to stimulate casein exocytosis. These results show that intracellular transport of prolactin and secretagogue effect of the hormone does not proceed at 25 degrees C. However, secretory mechanisms of the cell are always able to be stimulated by exogenous arachidonic acid at this temperature. Low temperature appears as a good means to study intracellular transport in the mammary cell.

Animals↗
PubMedDate not supplied

[Changes in secretion of prolactin in obesity].

The purpose of this study was to evaluate prolactin secretion in obesity. Basal level of serum prolactin and prolactin response after thyrotropin releasing hormone (TRH) were investigated in 20 obese patients and 20 healthy subjects well matched for age and sex. Obese patients had higher basal levels of serum prolactin than those of healthy subjects. Conversely, no significant difference in serum prolactin concentration was found at any time during TRH stimulating test. However obese patients showed incremental areas of serum prolactin slightly, but not significantly, lower compared to healthy subjects, probably because their basal levels were higher. In conclusion, the present study confirms that prolactin secretion is altered in obese patients. The discrepancy between basal levels and prolactin response during TRH stimulating test seems to indicate a deficiency in the dopaminergic inhibitor system.

Adult↗
PubMed1990

Effects of ammoniation of endophyte fungus-infested fescue hay on serum prolactin concentration and rectal temperature in beef cattle.

A group of 48 crossbred steers (approx 250 kg each) were used to determine the effects of various diets and treatments on serum prolactin concentrations and rectal temperatures. The steers were randomly assigned to groups fed the following: (1) endophyte fungus-infested fescue hay; (2) ammoniated endophyte fungus-infested fescue hay; (3) endophyte fungus-infested fescue hay plus 1 g of thiabendazole (TBZ)/9.1 kg of body weight at 7-day intervals; (4) ammoniated endophyte fungus-infested fescue hay plus 1 g of TBZ/9.1 kg at 7-day intervals; (5) ground Bermuda grass hay; and (6) endophyte-fungus-free fescue hay. Blood samples for prolactin determinations and rectal temperatures were obtained biweekly beginning on week 3 and continuing through week 9. A significant correlation (P less than 0.05) between low prolactin concentrations and high rectal temperatures in cattle eating endophyte-infested fescue hay was determined; however, as the prolactin concentrations approached normal (control animal) concentrations, this relationship between serum prolactin and rectal temperatures was not observed. Two antifungal agents used in this experiment (thiabendazole and ammonia) appeared to have different effects on the variables measured. Thiabendazole had no significant effect on prolactin concentrations or rectal temperatures of cattle ingesting endophyte-infested fescue hay, whereas ammoniation of this hay induced significantly higher (P less than 0.05) prolactin concentrations and lower rectal temperatures than in steers receiving only endophyte-infested fescue hay. Therefore, ammonia may be valuable not only as an aid in determining the cause of the fescue problem but also as a practical solution to some of the fescue-related economic problems in the cattle industry. Also, prolactin concentrations may be valuable in diagnosing fescue-related problems.

Acremonium↗
PubMedDate not supplied

Effects of serotonin-active drugs on prolactin secretion in male rats.

The effects of several serotonin acting drugs on serum prolactin levels were studied in male rats. Administration of the serotonin precursor, 5-hydroxytryptophan (5-HTP; 250 mg/kg ip) or pargyline (5 mg/kg ip) with 5-HTP (100 mg/kg ip) significantly increased serum prolactin concentration. Pretreatment of rats with the serotonin agonist, quipazine (10 mg/kg ip) caused increase in serum prolactin levels. Depletion of serotonin stores by pretreatment with p-chloro-phenylalanine methyl-ester (PCPA; 3 x 300 mg/kg ip) significantly prevent the effect of quipazine on prolactin levels. Serotonin uptake blocker, fluoxetine (10 mg/kg ip) produces an increase in the prolactin concentrations of the serum. Administration of the reserpine (2.5 mg/kg sc) did not affect serum prolactin levels. Both serotonin receptor blockers, cyproheptadine (0.5 mg/kg ip) and pizotifen (1 mg/kg ip) caused a week decrease in the serum prolactin levels. Significant changes in concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in brain of rats pretreated with above serotonin-active drugs were found. These results indicate that serotonergic system can modify secretion of prolactin.

Animals↗
PubMed1986

Phosphorylation of prolactin.

Rat prolactin exhibits microheterogeneity when examined in electrophoretic systems, running as three isoforms having the same molecular weight but different net charges (prolactins 1, 2, and 3 with isoform 3 being the most acidic). As there is precedent for the phosphorylation of a pituitary hormone and phosphorylation is a common cause of microheterogeneity, we examined the possibility that rat prolactin existed in differentially phosphorylated forms. The investigation included examinations of rat prolactin phosphorylation both in vitro and in vivo. For the in vitro studies, purified rat prolactin was incubated with [gamma-32P]ATP and low levels of each of five purified protein kinases. Phosphorylated rat prolactin was identified by autoradiography of silver-stained one- and two-dimensional gels. For the in vivo studies, rat anterior pituitary cells in primary culture were incubated in the presence of H3 32PO4 for 2 or 12 h, after which time the proteins were extracted from the cells, cold acetone-precipitated, or immunoprecipitated and run on two-dimensional gels. We report the in vitro phosphorylation of rat prolactin by cAMP-dependent protein kinase, casein kinase I, protease-activated kinase I, and the calcium/phospholipid-dependent kinase, that phosphorylation with these kinases results in phosphate incorporation only into isoforms 2 and 3, and the phosphorylation of prolactin in rat pituitary cells in primary culture.

Animals↗
PubMed1988

Stimulation of prolactin gene expression by insulin.

GH3 cells are a rat pituitary-derived cell line in which the expression of the growth hormone and prolactin genes is controlled by a variety of hormones including thyroid hormone. Since these cells contain insulin receptors, we explored whether these cells can be used to analyze the mechanisms involved in the regulation of gene expression by insulin. When GH3 cells were incubated with serum-free media, insulin stimulated prolactin production rates about 3-fold after 72 h and 10-fold after 96 h of incubation. Insulin stimulated prolactin mRNA levels and gene transcription rates to the same extent as the prolactin production rates. In contrast, insulin did not stimulate the rate of growth hormone production or growth hormone mRNA levels. As previously reported, thyroid hormone stimulated growth hormone production and mRNA levels. In these cells, thyroid hormone also stimulated prolactin synthesis and prolactin mRNA levels. Prolactin production and mRNA levels in cells incubated with both insulin and thyroid hormone showed a synergistic response which was about 5- to 10-fold greater than with either hormone alone. In contrast, growth hormone production rates in cells cultured with insulin and thyroid hormone was only slightly greater than cells incubated with only thyroid hormone. Half-maximal stimulation of prolactin production in cells incubated with insulin or with both insulin and thyroid hormone occurred between 2 and 5 nM insulin, suggesting that the response is mediated by the insulin receptor. These results indicate that GH3 cells should be useful in analyzing the mechanisms involved in regulation of gene expression by insulin.

Animals↗
PubMed1988

Prolactin release during nursing in early puerperium.

The changes induced in prolactin levels during the first 6 days following delivery were studied. Blood samples for prolactin assay were taken from 9 women at 5-min intervals during breast feeding. The levels of lactation were followed via the amounts of milk produced during suckling. The highest prolactin levels were observed on days 2-4 following delivery. There appeared to be some correlation between the basal and breast-feeding-induced prolactin levels and the level of lactation. A relatively low basal level and a moderate feeding-induced response are early indicators of delayed and less productive lactation. In unfavourable cases the feeding-induced prolactin increases gradually disappeared and lactation stopped. The correlation between the prolactin level and the quantity of milk formed is not a close one, but the observed tendencies agree with the role of prolactin. From day 5 on, the prolactin demands of the breasts are lower.

Female↗
PubMed1987

Effects of month and age on prolactin concentrations in stallion serum.

Prolactin concentrations in stallion serum were measured by a newly developed radioimmunoassay based on anti-dog prolactin serum and radiolabelled horse prolactin. Samples of serum from a total of 444 stallions were obtained at a commercial abattoir monthly from April to the following March. Ages of stallions were estimated from eruption and wear patterns of incisors. In the analysis of variance, both month (P less than 0.01) and age (P less than 0.05) were significant sources of variation whereas there was no interaction between these factors. Monthly means for prolactin concentrations were greatest between May and August with peak concentrations occurring in July (7.1 +/- 0.5 ng/ml). Lowest mean concentrations of prolactin (1.2 ng/ml) were observed during the winter months (December and January). Concentrations of prolactin were lowest in stallions less than or equal to 5 years old and were highest in stallions greater than 10 years old. It appears that prolactin secretion in the stallion is strongly influenced by season, as it is in the mare and in other seasonally breeding animals. Moreover, prolactin secretion in the stallion tends to increase as the stallion ages.

Aging↗
PubMed1986

Reduction of phosphatidylcholine turnover in a Nb 2 lymphoma cell line after prolactin treatment. A novel mechanism for control of phosphatidylcholine levels in cells.

Phosphatidylcholine metabolism was investigated in Nb 2 rat node lymphoma cells, a cell line which is dependent on prolactin for growth in culture. Treatment of stationary cultures with prolactin stimulated the incorporation of [methyl-3H]choline into phosphatidylcholine (1.7-fold after 4 h) and its aqueous precursors, mainly phosphocholine (1.9-fold after 4 h and 2.7-fold after 10 h). These effects were blocked by cycloheximide. Pulse-chase studies demonstrated that the reaction catalyzed by CTP:choline-phosphate cytidylyltransferase (EC 2.7.7.15) was rate-limiting for phosphatidylcholine synthesis in Nb 2 cells and that the rate of this reaction was not altered by prolactin treatment. The cell-free activity of choline kinase (EC 2.7.1.32) was found to increase in correspondence with the increase in choline incorporation. This induction of choline kinase was also blocked by cycloheximide. The activities of the other enzymes of phosphatidylcholine synthesis were unchanged. These results suggest that phosphatidylcholine biosynthesis was not altered in Nb 2 cells after prolactin treatment. However, phosphatidylcholine levels increased in prolactin-treated cells (1.4-fold after 16 h). Turnover of labeled phosphatidylcholine was markedly reduced in prolactin-treated cells. Calculated turnover rates for phosphatidylcholine averaged 4.2-fold lower in prolactin-treated cells, whereas the synthetic rates were similar in prolactin-treated and stationary cells. Thus, Nb 2 cells utilize a novel mechanism, reduction of turnover, to regulate the cellular levels of phosphatidylcholine during growth.

Animals↗
PubMed1985

[Prolactin in females with liver cirrhosis].

The median plasma level of prolactin in 94 women with cirrhosis of the liver did not differ significantly when compared with a control group (8,0 versus 7,2 ng/ml). Nevertheless 22% of the investigated women exhibited a plasma prolactin level higher than 15 ng/ml. The prolactin concentrations correlated to the severeness of cirrhosis and in the subgroup with decompensated cirrhosis the prolactin concentrations were found to be significantly elevated (12 ng/ml). Like basal prolactin the TRH-induced prolactin release showed no significant difference between cirrhotic women and controls (36,1 versus 38,5 ng/ml). No difference could be observed between the prolactin concentrations of alcoholic or non alcoholic cirrhotic women, and prolactin did not correlate with estradiol or estrone plasma levels. Other factors than cirrhosis itself (i.e. medical treatment, renal insufficiency, stress) must be discussed as causing hyperprolactinemia in cirrhosis.

Female↗
PubMed1979

Isolation and partial characterization of prolactin from equine pituitary gland (hypophysis).

Highly purified equine prolactin was prepared from equine pituitary glands (hypophysis) by serial extractions with water at pH 5.5, 0.1 M (NH4)2SO4 at pH 4.0, and 0.25 M (NH4)2SO4 at pH 5.5 to remove other hormones, and then finally with 70% ethanol at pH 9.3 to 10.0 to extract prolactin. Preliminary purification of the extract involved salting out other substances with 0.1% NaCl at pH 9.0. Prolactin was precipitated out by adding three times the volume of 95% ethanol at 4 C. This prolactin preparation had a biological potency of 24 IU/mg. Further purification by isoelectric focusing on a pH gradient of 5 to 7 gave three prolactin components with the following characteristics: isoelectric point 5.8, 5.7, and 5.25; biological potencies (IU/mg) 35.6, 19.6, and 11.3. The major component had a molecular weight of 25,000, an isoelectric point of 5.8, and a biological potency of 35.6 IU/mg. Antiserum produced against this component did not cross-react with equine follicular stimulating hormone, luteinizing hormone, and growth hormone, but did cross-react with ovine and bovine prolactin. Human and murine prolactin had little cross-reactivity with the equine prolactin antiserum.

Animals↗
PubMed1984

Chromatin structure, transcription, and methylation of the prolactin gene domain in pituitary tumors of Fischer 344 rats.

In order to study prolactin gene transcription and chromatin structure in a relatively homogeneous population of prolactin-producing cells, we induced lactotroph proliferation (pituitary tumor formation) in Fischer 344 rats by chronic diethylstibestrol treatment. We show that the prolactin gene is highly sensitive to digestion by DNase I in the chromatin of these pituitary tumors but not in liver. Furthermore, sequences immediately flanking the prolactin gene exhibit a similar high DNase I sensitivity. This contrasts with previous reports that the coding region of some genes is highly sensitive to DNase I digestion and that adjacent noncoding regions exhibit an intermediate sensitivity. This high level of DNase I sensitivity in the flanking regions was not due to transcription; we did not detect RNA transcripts homologous to any unique DNA sequence within 12 kilobase pairs upstream or downstream of the prolactin gene. We have identified two DNase I-hypersensitive sites 5' to the prolactin gene in pituitary tumors but none in liver. Also, the coding region, but not adjacent noncoding regions, of the prolactin gene domain is hypomethylated at MspI/HpaII and HhaI restriction enzyme sites in pituitary tumors. The prolactin gene domain is methylated at these sites in liver.

Animals↗