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Results for “PROLACTIN”

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At least 181 records · Page 10Linked to original sources

PubMed1997

Biochemical nature of high-molecular-weight prolactin of human serum: identification of a prolactin-binding protein.

The biochemical nature of a high-molecular-weight immunoreactive prolactin (HMW-irPRL) prepared by gel filtration of women's sera with predominance of this hormone form was studied. Immunochemical characteristics of HMW-irPRL are different from those of 23 kD prolactin (23 kD-PRL). A protein which specifically and reversibly binds to human [125I]PRL is isolated from the pooled fractions of HMW-irPRL by affinity chromatography on prolactin-Sepharose. According to gel filtration, the binding protein (BP) has molecular weight about 150 kD, and it reversibly binds to protein A immobilized on Sepharose. Analysis of BP by SDS-PAGE resulted in two major protein bands, of 65-70 and approximately 150 kD. Both the bands, when transferred to nitrocellulose, interacted with [125I]protein A. Binding of highly purified human pituitary prolactin to the BP significantly decreased the immunoreactivity of the hormone. The molecular weight of BP and its interaction with protein A and recognition by poly- and monoclonal antibodies against human (but not guinea pig) IgG indicate that BP may be an immunoglobulin. Thus, our data demonstrate that HMW-irPRL is formed by the binding of 23 kD-PRL to a specific serum protein which is probably an anti-prolactin IgG.

Adsorption↗

PubMed1983

Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: pre- and postpartum [125I]-prolactin binding activity.

Expression of specific [125I]-prolactin-binding sites under culture conditions has been investigated for isolated mammary epithelial cells from virgin, pregnant, and lactating rabbits. Primary monolayer cultures were obtained by sequential enzymatic dispersion of mammary tissue followed by 48 hr incubation in a medium selective for epithelial cells. Scatchard analyses of binding data obtained from these cultures indicated a single class of receptor sites, the affinity constant of which (2.5 X 10(9) M-1) did not vary significantly during mammary development. The number of prolactin receptors, however, expressed by virgin and early pregnant epithelial cells was significantly increased over those from late pregnancy or lactation. Less differentiated cells also respond to growth in pregnant rabbit serum with an increase in specific [125I]-prolactin binding. The diminished receptor expression by cells obtained after 17 days of pregnancy coincides with the attainment of secretory capacity in the animal, and may reflect the influence of the low serum prolactin or high progesterone levels circulating during the last trimester in the rabbit, or be the cultural expression of secretory differentiation.

Animals↗

PubMed1990

Effect of hypophysectomy, replacement therapy with ovine prolactin, and cortisol and triiodothyronine treatment on prolactin receptors of the tilapia (Oreochromis mossambicus).

The effects of hypophysectomy and subsequent replacement therapy with ovine prolactin (oPRL) on specific binding of 125I-oPRL to gill, kidney, and liver membranes of male tilapia were examined. The possible control of prolactin receptors by cortisol (F) and triiodothyronine (T3) was also studied using intact animals. In gill and kidney, hypophysectomy resulted in a significant decrease in specific binding that was partially restored (threefold increase) by three injections of oPRL, suggesting a role of the pituitary in the control of prolactin receptors. However, removal of the pituitary and replacement therapy with oPRL had no effect on binding by liver membranes. Cortisol and T3 treatment, alone or in combination, did not significantly affect prolactin binding by any of the tissues tested.

Animals↗

PubMed1994

Two monoclonal antibodies against prolactin-receptor are internalized in epithelial mammary cells without mimetic prolactin effect on casein secretion.

Prolactin exerts an early stimulatory effect on casein secretion which was qualified as a secretagogue effect. After binding to its receptor, the hormone transits intracellularly through the mammary epithelial cell. When this transit is slowed down the secretagogue effect does not occur. Different monoclonal antibodies which bind to the rabbit prolactin receptor have been previously developed. One of them (A917) mimics prolactin effect on casein gene expression. Another (M110) blocks this prolactin effect. In order to study the respective role of the hormone and its receptor, we have examined the binding of the two monoclonal antibodies (M110 and A917), labeled with biotin or colloidal gold, to the receptor of lactating rabbit mammary epithelial cells in incubation. Subsequently, the intracellular movement of these antibodies and the secretory response have been measured. Irrespective of the labeling (biotin or colloidal gold) or the preparation of tissues (fragments or enzymatically dissociated cells), M110 and A917 bound to the basal membrane of mammary epithelial cells. However, only M110 bound to apical membrane of dissociated cell when this membrane was in direct contact with the incubation medium, showing that the two antibodies discriminate the receptor located on the apical membrane. Following internalization, each antibody was carried via a peculiar pathway. M110 remained associated with the cells during a 1-h incubation, mainly in endosomes, multivesicular bodies and lysosomes like vesicles. In contrast, A917 was very quickly detectable in endosomes, multivesicular bodies and vesicles of the Golgi region and was carried throughout the cell to the lumen of the acini. M110 and A917 were extremely rare in secretory vesicles containing casein micelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Molecular cloning of the bovine prolactin receptor and distribution of prolactin and growth hormone receptor transcripts in fetal and utero-placental tissues.

We have isolated a bovine prolactin (bPRL) receptor cDNA from an endometrial cDNA library, which predicts a 557 amino acid transmembrane protein similar to the long forms of other characterized prolactin receptors. The predicted cytoplasmic domain is slightly truncated primarily by a stop codon located 36 codons 5' from the stop utilized in the human hepatic transcript. When expressed in COS cells, this cDNA was shown to encode a protein which bound bovine placental lactogen (bPL) and bPRL with nearly equal affinity (KD for bPL, 2.03 x 10(-10) M; bPRL, 3.07 x 10(-10) M). Northern analysis demonstrated multiple transcripts, with maternal liver, corpus luteum, intestine, endometrium and fetal liver containing a major transcript of about 3.8 kb, and maternal corpus luteum and endometrium, a second sized transcript of apparently equal abundance of 4.4 kb. This difference did not appear to be within the coding region. Primer extension analysis of maternal hepatic and endometrial transcripts revealed considerable heterogeneity. Examination of the distribution of prolactin and growth hormone receptor transcripts at mid-pregnancy by semi-quantitative reverse transcriptase polymerase chain reaction showed that both are widespread in bovine fetal and placental tissues. This isolation of bovine prolactin receptor cDNA, and description of receptor distribution will facilitate study of the action of the placental and pituitary members of this gene family during pregnancy.

Amino Acid Sequence↗

PubMed2000

Puerperal alactogenesis with normal prolactin dynamics: is prolactin resistance the cause?

OBJECTIVE: To determine the cause of puerperal alactogenesis in a young woman. DESIGN: After proper clinical assessment, a definitive investigative protocol was followed to determine the cause of alactogenesis. SETTING: Tertiary care medical center in Kashmir, India. PATIENT(S): A young married woman with three full-term deliveries, all characterized by puerperal alactogenesis. INTERVENTION(S): An investigative protocol to document prolactin reserve and mammography to demonstrate presence of normal breast tissue. MAIN OUTCOME MEASURE(S): Prolactin secretory reserve. RESULT(S): The patient had normal breast development and an adequate pituitary prolactin reserve. CONCLUSION(S): Prolactin resistance may have caused alactogenesis.

Adult↗

PubMed1986

Modulation of testicular receptors for LH, FSH and prolactin by the administration of ovine prolactin in mature rat.

To elucidate the role of prolactin on testicular function, we treated mature rats with ovine prolactin (oPRL) and investigated the dose and time-dependent changes in testicular LH, FSH and prolactin receptors as well as in serum gonadotropin and steroid levels. Twelve week-old rats were injected sc with a single dose of various amounts of oPRL (0.2, 1 and 5 IU) and killed on the first, second and third days after the treatment. Testicular LH receptor decreased to 59% of the control level as a function of time while prolactin receptor increased to 244% maximally of the control level on the second day. In contrast, FSH receptor changed in a different fashion. Smaller amounts of oPRL (0.2 and 1 IU) raised the receptor level to 193% of the control level on the first day whereas a larger amount (5 IU) did not change the receptor, which tended to remain in a low level throughout the experimental period. The serum FSH level significantly increased in every group on the second day, then returned to the control range by the third day. On the other hand, the serum testosterone level changed in a characteristic manner, decreased significantly in every group on the first day though not in a dose-dependent fashion, returned to normal on the second day and significantly increased in the 0.2 IU group on the third day (p less than 0.01). Similarly, the serum estradiol level decreased in the oPRL-treated groups on the first day and was restored on the second day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1976

Effect of prolactin and the anit-prolactin bromocriptin on the testosterone uptake and metabolism in androgen-sensitive and insensitive canine organs.

Prolactin promotes the growth and function of the prostate in low doses, whereas high doses or previous castration reduce this effect. The antiprolactin bromocriptin should reverse the prolactin action. In the castrated dog the highest accumulation of H3-testosterone given i.v. occurred in the prostate as compared with muscle, urethra, penis, liver and kidney. Prolactin pretreatment increased the radiosteroid uptake only in the liver. Converseley, bromocriptin suppressed the tracer incorporation into the liver, but increased prostatic accumulation. The highest testerone reduction occurred in the prostate of the untreated castrated dogs as compared with other organs. Prolactin suppressed 5 alpha -dihydrotestosterone formation but otherwise did not significantly influence testosterone turnover. Bromocriptin, however, stimulated dihydrotestosterone formation in the prostate and caused complete inhibition of hepatic testosterone reduction.

Animals↗

PubMed1976

Prolactin in amniotic fluid: its correlation with maternal plasma prolactin.

Prolactin concentrations in amniotic fluid from 319 women with normal pregnancies and 29 women with complicated pregnancies were determined by radioimmunoassay. Prolactin levels varied from 36 ng/ml to 1800 ng/ml mean +/- S.D. = 408 +/- 297) in the normal pregnancy group but showed no definite pattern of rise or fall during pregnancy. No difference in levels was found in complicated pregnancies. Prolactin concentrations in the plasma from 203 of these women were also assayed. The levels in the amniotic fluid were about 9 fold higher than those in the plasma. There was no significant correlation between amniotic fluid and plasma levels of prolactin.

Amniotic Fluid↗

PubMed1988

Monoclonal antibodies specific for non-glycosylated porcine prolactin and for pituitary porcine prolactin.

Glycosylated and non-glycosylated forms of porcine pituitary prolactin were prepared using Concanavalin A Sepharose chromatography. Anti-prolactin monoclonal antibodies were screened for their ability to distinguish these two forms. One monoclonal antibody (17D9) exhibited high affinity binding for the non-glycosylated form of porcine prolactin, but little or no affinity for the glycosylated form. Using this antibody in conjunction with other monoclonals which equally recognize both forms, we developed immunoassays which can be used to determine the amount of the glycosylated vs. non-glycosylated prolactin in serum or other tissue samples.

Animals↗

PubMed2001

Prolactin receptor gene expression and immunolocalization of the prolactin receptor in human luteinized granulosa cells.

Prolactin is mainly known for its role in breast development and lactation, but has been also implicated in other physiological functions such as immunoregulation and ovarian steroid production. Although prolactin and prolactin receptor (PRL-R) transcripts have been previously identified in the human ovary, the spatial localization of the receptor is unknown. To investigate the presence of PRL-R within the follicular apparatus, human luteinized granulosa cells were obtained at the time of follicular aspiration from women undergoing ovarian stimulation for IVF. RNA extracted from these cells was subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) using specific primers for the PRL-R gene. In addition, paraffin sections of isolated granulosa cells and sections of premenopausal human ovaries were immunostained with a mouse anti-human PRL-R monoclonal antibody. PRL-R were immunolocalized to the cell membrane of isolated luteinized granulosa cells and PRL-R transcripts were detected in the extracted RNA. No detectable staining was noted in secondary and early antral follicles in archived paraffin sections. These findings confirm the presence of PRL-R in human luteinized granulosa cells and suggest a localized role for PRL within the mature follicle. The absence of PRL-R in the early follicle suggests that the effects of prolactin are exerted around the time of ovulation.

Adult↗

PubMed1980

Chlorpromazine, haloperidol, metoclopramide and domperidone release prolactin through dopamine antagonism at low concentrations but paradoxically inhibit prolactin release at high concentrations.

1. The effects of chlorpromazine, haloperidol, metoclopramide and domperidone on the release of prolactin from perfused columns of dispersed rat anterior pituitary cells were studied. 2. Chlorpromazine, haloperidol, metoclopramide and domperidone antagonized the dopamine-mediated inhibition of prolactin release at low concentrations. 3. Each dopamine antagonist displaced the dose-response curve for dopamine-induced suppression of prolactin release to the right in a parallel manner. 4. At higher concentrations, the four drugs became less effective as dopamine antagonists. 5. At high concentrations in the absence of dopamine, chlorpromazine, haloperidol, metoclopramide and domperidone paradoxically suppressed prolactin secretion by an unknown mechanism.

Animals↗

PubMed2001

Pituitary production of prolactin and prolactin-suppressing drugs.

Prolactin secretion from the anterior pituitary is mediated via dopaminergic pathways. Any process that alters dopamine production or transport in the central nervous system may lead to hyperprolactinemia. Most cases of hyperprolactinemia are due to prolactin secreting pituitary tumors or to medications which alter dopamine production. Prolactinomas cause amenorrhea, galactorrhea and infertility in women and impotence and neurological deficits in men. Dopamine receptor agonists are the mainstay of therapy for hyperprolactinemia as they rapidly lower serum prolactin and cause tumor shrinkage. In this paper we review the regulation of prolactin secretion, the clinical features and causes of hyperprolactinemia, and the use of dopamine agonists.

Dopamine Agonists↗

PubMed1977

Dopamine enhances the action of prolactin on rat blood vessels. Implications for dopamine effects on plasma prolactin.

It has been claimed that dopamine enhances peripheral uptake of prolactin. Dopamine at 2.1 x 10(-9)M, a concentration which had no effect by itself, enhanced both the potentiation of rat mesenteric vascular reactivity caused by 50ng/ml ovine prolactin and the inhibition of reactivity caused by 500ng/ml prolactin. These observations are consistent with the proposal that dopamine can interact peripherally with prolactin.

Animals↗

PubMed1980

[A measurement of immunoreactive prolactin in the decidual and villous tissues of early pregnancy, and a comparison with the prolactin in the amniotic fluid (author's transl)].

Several reports have revealed that human prolactin increases during pregnancy, not only in maternal and fetal serum but also in the amniotic fluid. The source and the role of prolactin in the amniotic fluid however, have not been clear up to now. In their incubation experiment, Riddick et al (29) proved that decidual tissue at term could secret immunoreactive prolactin (IR-PRL). In order to investigate the source of PRL in the amniotic fluid, we extracted IR-PRL from decidual or villous tissue in early normal pregnancies and measured it by a double antibody radioimmunoassay in this experiment. The results were the following: 1) We were able to measure IR-PRL from decidual or villous tissue in early pregnancy, the dilution curve of which paralleled pituitary standard prolactin. The cross reaction of a PRL standard preparation with HCG and HPL was not recognized within 10 micrograms/ml. 2) In human decidual tissue, the IR-PRL concentration began to increase at about the sixth week, arrived at the peak value, 81.06 +/- 2.13 ng/0.1 g dry weight (d.w.) in the eighth week, and did not change significantly after that. In human villous tissue, although the IR-PRL concentration was distinctly lower than it was in the decidual tissue, it increased gradually and reached the level of 37.44 +/- 7.16 ng/0.1g d.w. in the tenth week. 3) The extracted material (IR-PRL) from these two tissues in the 8th week, amniotic fluid at term, and pituitary standard PRL were passed through a Sephadex G-100 column (2 X 93 cm) with phosphate buffer and saline (0.01M, PH 7.4). In the chromatogram of these four test materials, one peak of IR-PRL was observed. The peak of IR-PRL of decidual and villous tissues and amniotic fluid revealed almost the same fraction number but elevated after the pituitary PRL preparation. 4) By gel filtration, the IR-PRL was able to be differentiated from HCG but not from HPL. The peak of HCG appeared earlier than the peak of IR-PRL and HPL. 5) The distribution of IR-PRL between human decidual and villous tissues was significantly different from that of HPL. IR-PRL concentration was higher in the decidual tissue than in the villous tissue, while HPL concentration was higher in the villous tissue than it was in the decidual tissue. From this observation, we could consider that the sources of these two hormones were different. The results of these experiments suggest that one of the sources of PRL in the amniotic fluid was the decidual tissue.

Amniotic Fluid↗

PubMed1981

Prolactin content in rat pituitary gland. RIA of prolactin after different extraction procedures.

The prolactin content of rat pituitary varies considerably when determined by RIA, due to incomplete solubilization of prolactin secretory granules with standard procedures for tissue homogenization and centrifugation. Freezing and thawing, Triton X-100 and ultrasonic treatments increased the yield of prolactin significantly but electron microscopy of pellets revealed numerous unmodified secretory granules. Addition of 2.5 M urea produced complete extraction of tissue prolactin confirmed by RIA of supernatants and electron microscopy of pellets.

Animals↗

PubMed1998

Ontogeny of the opioidergic regulation of LH and prolactin secretion in lactating sow. I: failure of naloxone to antagonize suckling-induced changes in LH and prolactin secretion in early lactation, irrespective of pattern of administration.

The principal aim of this study was to investigate the ontogeny of an opioidergic mechanism mediating the suckling-induced inhibition of LH secretion during lactation in sows. In contrast to an increase in LH secretion in response to naloxone treatment on days 10 and 11 of lactation (P < 0.05), a single injection of 2 mg naloxone kg-1 at 39, 51, 63, or 75 h post partum had no effect. However, the last of four injections of 2 mg naloxone kg-1 given at 12 h intervals to group IV sows did elicit a positive LH response (P < 0.05). Multiple injections of 1 mg naloxone kg-1 at 3 h intervals over 30 h on day 10-11 consistently increased (P < 0.05) mean plasma LH with no evidence of induced refractoriness to repeated use of the antagonist. Similarly, naloxone did not affect mean plasma prolactin in the immediate postpartum period, but either repeated naloxone treatments on day 10-11 or single naloxone injections on day 10 or 11 of lactation decreased plasma prolactin (P < 0.05). Therefore, the regulation of LH and prolactin secretion in lactating sows changes with time post partum. An opioid-dependent mechanism is an important component of the suckling-dependent regulation of LH and prolactin secretion in established lactation, but not during the first 72 h postpartum period.

Animals↗

PubMed1985

[Measurement of serum prolactin and the effect of ketamine anesthesia on serum prolactin levels in cynomolgus monkeys (Macaca fascicularis)].

The effect of an anesthetic, ketamine, on the serum prolactin level was examined in wild-originating female cynomolgus monkeys (Macaca fascicularis) imported from South East Asia. Serum prolactin levels were measured by the homologous radioimmunoassay system which was developed for human prolactin. The validity was confirmed by using an extract of pituitary gland from a female cynomolgus monkey as well as serum and amniotic fluid from a pregnant monkey. Additionally, serum luteinizing hormone (LH) levels were determined by the radioreceptor assay system developed in our laboratory using Leydig cells collected from rat's testes as a receptor fraction. The experiment was repeated three times at one-month interval, using twenty animals that were divided into three groups consisting of 5, 7 and 8 monkeys each. In the first experiment, the first group was injected with physiological saline and the second and third groups were intramuscularly given ketamine at a dose level of 5 mg/kg B.W. and 15 mg/kg B.W., respectively. In the second experiment, the first and second groups were given ketamine at a dose of 5 mg/kg B.W. and of 15 mg/kg B.W., respectively, and the third group was served as control injected with saline. In the third experiment, the first and third groups were administered with 15 mg/kg and 5 mg/kg of ketamine and the second group was injected with saline. In short, all of the twenty monkeys received the three different treatments for two months. The serum prolactin level showed a marked increase after the administration of ketamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗