Prolactin Receptor mRNA Levels Research Articles

Prolactin acts in the pathway of photoperiod regulating the reproduction of the Striped Hamsters

To study the effects of prolactin (PRL) in pituitary on the reproduction of the Striped Hamsters via the photoperiods. Mature female striped hamsters were raised under various photoperiods to study the differential expression pattern of PRL in pituitary, and prolactin receptor (PRLR) in the hypothalamus, pituitary and ovary. Photoperiods affect the pituitary PRL mRNA level and pituitary, hypothalamus and ovaries PRLR mRNA levels in striped hamsters. Positive correlations of PRL mRNA expression in the pituitary with that of PRLR in hypothalamus and ovaries, and that of GnRH in hypothalamus were determined. The serum concentration of PRL, FSH, LH and GnRH were significantly different among the striped hamsters from different photoperiods. Serum concentration of PRL is positively correlated with that of FSH, LH and GnRH of the striped hamsters. Photoperiod was important environment factor modulating the expression profile of PRL and PRLR in the striped hamsters.

Divergent genes encoding the putative receptors for growth hormone and prolactin in sea lamprey display distinct patterns of expression

Growth hormone receptor (GHR) and prolactin receptor (PRLR) in jawed vertebrates were thought to arise after the divergence of gnathostomes from a basal vertebrate. In this study we have identified two genes encoding putative GHR and PRLR in sea lamprey (Petromyzon marinus) and Arctic lamprey (Lethenteron camtschaticum), extant members of one of the oldest vertebrate groups, agnathans. Phylogenetic analysis revealed that lamprey GHR and PRLR cluster at the base of gnathostome GHR and PRLR clades, respectively. This indicates that distinct GHR and PRLR arose prior to the emergence of the lamprey branch of agnathans. In the sea lamprey, GHR and PRLR displayed a differential but overlapping pattern of expression; GHR had high expression in liver and heart tissues, whereas PRLR was expressed highly in the brain and moderately in osmoregulatory tissues. Branchial PRLR mRNA levels were significantly elevated by stage 5 of metamorphosis and remained elevated through stage 7, whereas levels of GHR mRNA were only elevated in the final stage (7). Branchial expression of GHR increased following seawater (SW) exposure of juveniles, but expression of PRLR was not significantly altered. The results indicate that GHR and PRLR may both participate in metamorphosis and that GHR may mediate SW acclimation.

Analysis of prolactin receptor expression in breast cancer subtypes

Breast cancer (BC) is the most common cancer among women. It is known that the prolactin receptor (PRLR) may play a role in breast carcinogenesis, but the available data are often contradictory. To get a more complete picture of the relationship between the receptor and mammary gland carcinogenesis, we examined the association between changes in PRLR expression level and tumor subtype (and its main characteristics). To do this, using real-time PCR, we evaluated the level of PRLR mRNA in BC tissue samples and untransformed adjoining tissue samples (89 pairs). Since the androgen receptor (AR) has begun to be seen as a prognostic marker in breast cancer, we also evaluated the association between mRNA levels of AR and PRLR. We found a significant increase in PRLR expression in luminal subtypes; the highest level of PRLR mRNA was detected in luminal A subtype. In HER2-positive ER-, PR-negative BC, the PRLR mRNA level decreases in tumor tissues compared with untransformed tissues. High PRLR expression is also associated with smaller tumor size in luminal B HER2-negative subtype. In ER-, PR-negative tumors, PRLR expression is associated with AR expression: PRLR mRNA level is increased when AR mRNA level is reduced by more than 8 times in triple-negative tumors; in contrast, in HER2-positive subtype it decreases more significantly when AR expression is reduced by more than 3 times. A tendency towards an increase in PRLR expression with an increase in the AR mRNA level was also discovered in luminal subtypes. The level of PRLR expression depends on the age of patients. In luminal A, PRLR expression is higher in patients under 65 years. In contrast, in luminal B HER2-negative and triple-negative BC, reduced PRLR expression was observed in patients under the age of 40 years and under the age of 50 years, respectively. In this group of patients under the age of 40 years with luminal B HER2-negative BC, ER expression was also reduced (0-4 score according to the IHC assay). Thus, PRLR probably plays a different role in the development and progression of BC: in luminal A and luminal B HER2-positive subtypes PRLR may act as an oncogen, and in luminal B HER2-negative and ER-, PR-negative subtypes can play a tumor suppressor role.

Expression of Prolactin Receptor mRNA in Lactotrophs and Somatotrophs of the Chicken Anterior Pituitary Gland.

Prolactin (PRL) is a hormone mainly secreted by the anterior pituitary gland. In birds, PRL exerts a variety of physiological functions in target tissues expressing the PRL receptor (PRLR). In chicken, the PRLR mRNA is abundant in the anterior pituitary gland, but its regional and cellular localization are unknown. In the present study, we investigated the expression of the PRLR mRNA in cephalic and caudal lobes of the chicken anterior pituitary gland. Real-time polymerase chain reaction (PCR) revealed high levels of PRLR mRNA in both cephalic and caudal lobes. In situ hybridization revealed that the PRLR mRNA was distributed in a wide area of both lobes, and co-localized with the PRL and growth hormone (GH) mRNAs in the cephalic and caudal lobes, respectively. These results suggest that PRL exerts autocrine/paracrine effects through PRLR on PRL-producing lactotrophs and GH-producing somatotrophs in the chicken anterior pituitary gland.

Dynamic responses of prolactin, growth hormone and their receptors to hyposmotic acclimation in the olive flounder Paralichthys olivaceus

Prolactin (PRL) and growth hormone (GH) play important roles in regulating salt and water balance through osmoregulatory organs in vertebrates. The aim of this study was to investigate the dynamic changes of GH/PRL hormone gene expressions in the pituitary gland and their receptors in gill and kidney, as well as the plasma osmolality when the olive flounder fish Paralichthys olivaceus were acclimated in freshwater (FW) conditions. After transfer from seawater (SW) to freshwater (FW), the osmolality of FW-adaption fish reached the lowest level at 1d which rose slightly afterwards. However, the hormone gene expression of PRL increased from 2d, reaching its peak at 5d, and then decreased at 14d. At this time, the value was still significantly higher than the control, showing a similar trend to the plasma hormone PRL. In contrast, the pituitary mRNA level of GH significantly decreased at 1d and then returned to normal levels. The mRNA levels of PRL receptor (PRLR) in both gill and kidney displayed a similar trend to the pituitary PRL. We also observed the synchronous expression trend of the renal PRLR with pituitary PRL (5d) and the asynchronous expression peaks between branchial (8d) and renal PRLR (5d). Significant responses of GH and its receptor (GHR) in both gill and kidney during the FW-acclimation were not observed. Nevertheless, the gene expression of GH receptor variant (GHR-V) in both gill and kidney declined at 2d, indicating unknown osmoregulatory functions of GHR-V. Collectively, our results provided more insights of the PRL, GH and their corresponding receptors in modulating osmoregulatory responses, representing an important aspect of FW–acclimation in flounder fish.

Effects of High-Fat Diet on Stress Response in Male and Female Wildtype and Prolactin Knockout Mice.

Prolactin (PRL) is well characterized for its roles in initiation and maintenance of lactation, and it also suppresses stress-induced responses. Feeding a high-fat diet (HFD) disrupts activity of the hypothalamic-pituitary-adrenal (HPA) axis. Whether PRL regulates HPA axis activation under HFD feeding is not clear. Male and female wildtype (WT) and PRL knockout (KO) mice were fed either a standard low-fat diet (LFD) or HFD for 12 weeks. Circulating corticosterone (CORT) levels were measured before, during, and after mice were subjected to an acute restraint stress or remained in their home cages as no stress controls. HFD feeding increased leptin levels, but the increase was lower in KO than in WT mice. All stressed female groups and only LFD-fed stressed males had elevated CORT levels compared to their no stress same-sex counterparts regardless of genotype. These results indicated that HFD consumption blunted the HPA axis response to acute stress in males but not females. Additionally, basal hypothalamic CRH content was lower in HFD than LFD males, but was similar among female groups. Furthermore, although basal CORT levels were similar among KO and WT groups, CORT levels were higher in KO mice than their WT counterparts during stress, suggesting that loss of PRL led to greater HPA axis activation. Basal PRL receptor mRNA levels in the choroid plexus were higher in HFD than LFD same-sex counterparts, suggesting activation of central PRL’s action by HFD feeding in both males and females. Current results confirmed PRL’s roles in suppression of the stress-induced HPA axis activation. Although HFD feeding activated central PRL’s action in both sexes, only the male HPA axis was dampened by HFD feeding.

Seasonal Expression of Prolactin Receptor in the Scented Gland of Male Muskrat (Ondatra zibethicus).

Prolactin (PRL) has numerous actions in mammalian biological systems including mammary development and biological processes. The aim of this study was to investigate the seasonal changes of prolactin receptor (PRLR) expression in the scented gland of muskrat during the breeding and nonbreeding seasons. Histologically, glandular cells, interstitial cells and excretory tubules were identified in the scented glands in both seasons, whereas epithelial cells were sparse in the nonbreeding season. PRLR was observed in glandular cells of scented glands during the breeding and nonbreeding seasons with stronger immunostaining during the breeding season. Consistent with the immunohistochemical results, both the mean of protein and mRNA levels of PRLR were higher in the scented glands of the breeding season, and relatively lower level in the nonbreeding season. In addition, differential seasonal changes were also detected in the expression profile of microRNAs (miRNAs) in the scented gland of muskrat. Besides, plasma PRL concentration was remarkably higher in the breeding season than that in the nonbreeding season. These results suggested that muskrat scented gland was the direct target organ of PRL, and stronger expression of PRLR in scented glands during the breeding season indicated that PRL may directly regulate scented glandular function of the muskrats.

Evidence of a role for prolactin as regulators of ovarian follicular development in goose

Background: Prolactin (PRL) regulates development and reproduction, and its effects are mediated by the prolactin receptor (PRLR). In order to clarify the role of PRLR and PRL in the process of follicular development in the goose ovary, the level of PRLR mRNA expression in the ovary and follicles of the Sichuan white goose was determined, as well as the PRL concentration in ovarian follicles. Results: The level of PRLR mRNA in the hierarchical follicles (HFs) initially increased, and subsequently decreased, whereas PRLR expression was initially low and later increased in postovulatory follicles (POFs). The level of PRLR mRNA expression was the highest in the F4 follicles, and lowest in the F1 follicles in all of the examined follicles. Compared with the level of PRLR mRNA expression in the small white follicles (SWFs), the level of PRLR mRNA was 2.86- and 1.44-fold higher in the F4 and small yellow follicles (SYFs), respectively (P Conclusions: The change of PRL concentration was similar to the PRLR mRNA expression level in preovulatory follicles. These results suggest that the PRL mediated by the PRLR plays a stimulatory role in the SWF to SYF transition.

Human and murine prostate basal/stem cells are not direct targets of prolactin

Local overexpression of prolactin (PRL) in the prostate of Pb-PRL transgenic mice induces benign prostate tumors exhibiting marked amplification of the epithelial basal/stem cell compartment. However, PRL-activated intracellular signaling seems to be restricted to luminal cells, suggesting that basal/stem cells may not be direct targets of PRL. Given their described role as prostate cancer-initiating cells, it is important to understand the mechanisms that regulate basal/stem cells. In this study, we evaluated whether PRL can act directly on these cells, by growing them as prostaspheres. For this, primary 3D prostasphere cultures were prepared from unfractionated cells isolated from freshly harvested human and mouse benign prostate tissues and subjected to PRL stimulation in vitro. None of the various concentrations of PRL tested showed any effects on the sizes or numbers of the prostaspheres generated. In addition, neither activation of canonical PRL-induced signaling pathways (Stat5, Stat3 or Erk1/2) nor increased expression of the proliferation marker Ki-67 were detected by immunostaining in PRL-stimulated prostaspheres. Consistent with the absence of response, PRL receptor mRNA levels were generally undetectable in mouse sphere cells. We conclude that human and mouse prostate basal/stem cells are not direct targets of PRL action. The observed amplification of basal/stem cells in Pb-PRL prostates might be due to paracrine mechanisms originating from PRL action on other cell compartments. Our current efforts are aimed at unraveling these mechanisms.

MRNA expression of prolactin receptor in sheep pituitary and its effect on maternal behavior.

Prolactin receptor (PRLR) is the specific receptor for prolactin. Brain-specific control of PRLR gene expression is correlated with the induction of maternal behavior. The aim of this study was to investigate the dynamic changes in the PRLR mRNA level in the sheep pituitary gland and its effect on ewe maternal behavior. The mRNA expression of PRLR during non-pregnancy stage was maintained at low but detectable levels, as was the case during mid-gestation. After that, expression began increasing and reached a maximum during the early postpartum followed by a gradual decline during the mid-postpartum and late postpartum stages. A trend of higher PRLR mRNA expression was observed during the postpartum stage relative to the non-pregnancy and pregnancy stages. Expression of PRLR mRNA was significantly higher in the normal maternal behavior group than that in the abnormal maternal behavior group. There may be a correlation between PRLR mRNA expression and ewe maternal behavior, especially in early postpartum.

Effects of acupuncture on progesterone and prolactin in rats of embryo implantation dysfunction.

To investigate the effect of acupuncture on progesterone (P4) and prolactin (PRL) in rats of embryo implantation dysfunction (EID). On the first day of pregnancy, 72 female Wistar rats were randomly allocated into the normal group, the EID model group, the acupuncture group and the P4 group (18 in each group). The normal group was injected sesame oil, while the other three groups were given mifepristone to establish the EID model. The acupuncture group and the P4 group were given treatment of acupuncture and P4 injection, respectively. The serum of P4 and PRL were detected by radioimmunoassay, and the mRNA and protein expressions of P4 receptor (PR) and PRL receptor (PRLR) were detected using real-time polymerase chain reaction and immunohistochemical method, respectively. Compared with the normal group, the serum levels of P4 and PRL as well as the mRNA and protein expression levels of PR and PRLR in the EID model group were significantly lowered (P<0.01 or P<0.05). The above indices in the acupuncture group and the P4 group were significantly elevated compared with the EID model group (P<0.01 or P<0.05). Acupuncture can promote embryo implantation effectively, which might be related to the effects of acupuncture on upregulating the P4 and PRL levels in serum and the PR and PRLR expression levels in rats.

MRNA expression, polymorphism of prolactin receptor gene and their association with prolificacy in Lezhi black goats

mRNA expression and DNA polymorphism of prolactin receptor (PRLR) gene were investigated and used to study their effects on litter size in goats. Real-time polymerase chain reaction (PCR) analysis revealed that PRLR mRNA levels in pituitary and endometrium of prolific Lezhi black goats were 39.0-fold and 29.9-fold higher than those in non-prolific Tibetan goats (P < 0.05), but there was no difference in ovary and liver between the two breeds. To further explore the possible association between variations in PRLR gene with litter size in Lezhi black goat, mutation screening of exon 10 of PRLR was performed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). In P2 locus, the four genotypes AA, AB, AC, and AD had the genotypic frequencies of 0.136, 0.110, 0.162, and 0.594, respectively, but no polymorphism was detected in P1 locus. There were four mutations at C89T, A94C, C146G, and G157C of this fragment in all of the four genotypes, which led to a missense mutation Pro to Leu, Asn to His, Ala to Gly, and Ala to Pro, respectively. In addition, a mutation of C61T in genotype AA, A175G in genotype AD, T24C and C96T in genotype CD were detected. The Lezhi black does with genotype AD had 0.35 (P < 0.05) more kids than those with genotype AB, but there was no significant difference among other genotypes. It is concluded that PRLR gene expression and mutations in exon 10 of PRLR gene may be associated with the reproductive effects of the Lezhi black goat.

Prolactin regulates TRPV1, TRPA1, and TRPM8 in sensory neurons in a sex-dependent manner: Contribution of prolactin receptor to inflammatory pain

Prolactin (PRL) is a hormone produced in the anterior pituitary but also synthesized extrapituitary where it can influence diverse cellular processes, including inflammatory responses. Females experience greater pain in certain inflammatory conditions, but the contribution of the PRL system to sex-dependent inflammatory pain is unknown. We found that PRL regulates transient receptor potential (TRP) channels in a sex-dependent manner in sensory neurons. At >20 ng/ml, PRL sensitizes TRPV1 in female, but not male, neurons. This effect is mediated by PRL receptor (PRL-R). Likewise, TRPA1 and TRPM8 were sensitized by 100 ng/ml PRL only in female neurons. We showed that complete Freund adjuvant (CFA) upregulated PRL levels in the inflamed paw of both male and female rats, but levels were higher in females. In contrast, CFA did not change mRNA levels of long and short PRL-R in the dorsal root ganglion or spinal cord. Analysis of PRL and PRL-R knockout (KO) mice demonstrated that basal responses to cold stimuli were only altered in females, and with no significant effects on heat and mechanical responses in both sexes. CFA-induced heat and cold hyperalgesia were not changed in PRL and PRL-R KO compared with wild-type (WT) males, whereas significant reduction of heat and cold post-CFA hyperalgesia was detected in PRL and PRL-R KO females. Attenuation of CFA-induced mechanical allodynia was observed in both PRL and PRL-R KO females and males. Thermal hyperalgesia in PRL KO females was restored by administration of PRL into hindpaws. Overall, we demonstrate a sex-dependent regulation of peripheral inflammatory hyperalgesia by the PRL system.

The phytoestrogen daidzein may affect reproductive performance of Zhedong White geese by regulating gene mRNA levels in the HPG axis

1. The effect of daidzein, a naturally occurring phytoestrogen, on the reproductive performance of 120 female Zhedong White geese was determined. The geese were divided into 4 groups which were fed on diets containing 0 (Control), 10 (Da1), 20 (Da2) and 30 (Da3) mg daidzein per kg diet. Egg production and weight, fertility and hatchability rates, concentrations of estradiol (E2), triiodothyronine (T3), progesterone (P4), thyroxine (T4) and growth hormone (GH) in serum, and mRNA levels of gonadotropin releasing hormone (GnRH), β-follicle stimulating hormone (FSHβ), follicle stimulating hormone receptor (FSHR), oestrogen receptor1 (ESR1), oestrogen receptor2 (ESR2), prolactin (PRL), prolactin receptor (PRLR), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the hypothalamus-pituitary-gonadal axis (HPGA) were measured.2. Daidzein increased egg weight and fertility but had no detectable effect on egg production and hatchability.3. Daidzein affected serum P4 and GH concentrations and T4 rhythm, up-regulated GnRH mRNA and PRLR mRNA levels in the hypothalamus, down-regulated PRLR mRNA in the hypothalamus, PRL mRNA in the pituitary, and ESR2 mRNA levels in the ovary, respectively. The mRNA rhythms of PRLR in the hypothalamus, PRL, PRLR and FSHβ in the pituitary, FSHR, ESR1 and ESR2 in the ovary were significantly changed in the Da2 group.4. It is suggested that an appropriate dose of daidzein might improve reproductive performance by affecting serum hormone concentrations and rhythms and regulating gene mRNA levels in the HPGA of female Zhedong White geese.

In vitro Suppression of Prolactin During Later Stages of Egg Lay in Domestic Hen (Gallus gallus Domesticus) Anterior Pituitcytes by RNA Interference

2 Abstract: Prolactin (PRL) is a peptide hormone secreted by anterior pituitary gland. PRL increases as per the age and reproductive cycle of birds from normal physiological levels to extremely higher level there by affecting the ovulation, egg formation, oviposition, egg production and hyperprolactinemia. This is mor e pronounced and persistent after 72 weeks of age in birds. Hence a study was conducted in anterior pituitary primary cultured cells obtained from 72 and 82 weeks old white leg horn (WLH) hens to knock down the PRL gene expression by siRNA and observing its effects on PRL, PRL mRNA, protein content of PRL, prolactin receptor (PRLR) and Growth Hormone (GH) mRNA to unravel the functional role of PRL at 72 and 82 week age by siRNA for PRL. Three siRNAs were designed as per standard siRNA protocols and studied the suppression of PRL gene expression in primary cultured cells procured from adult chicken anterior pituitary glands in in vitro conditions. Average percentage reduction of PRL in anterior pituitary primary cell culture following siRNA transfection was 82 and 60% at 72 and 82 weeks respectively. Protein content of PRL was significantly (p<0.01) decreased in siRNA transfected cells compared to controls. Growth Hormone (GH) mRNA and PRL receptor (PRLR) mRNA levels did not change significantly (p<0.01) between control and treated cells. Results clearly suggested that the siRNA designed for PRL specifically decreased PRL gene expression in in vitro conditions. Level of PRLR mRNA and GH mRNA levels expression did not follow the similar pattern of PRL gene expression in anterior pituitary cells. It is concluded that, construction of short specific siRNA for PRL significantly decreased PRL, PRL mRNA and protein content of PRL without showing any effect on PRLR and GH between the two age groups of birds. These results may lead to construction of short specific siRNA for stable and chronic suppression of PRL gene expression during embryogenesis before an increase of PRL occurs for long term knock down of PRL in in vivo conditions. In conclusion , understanding of hyperprolactinemia and the involvement of PRL may provide the basis for the development of therapeutic drugs or methods against hyperprolactinemia by RNA interference.

Regulation of Prolactin Receptor Gene Expression in the Rat Choroid Plexus via Transcriptional Activation of Multiple First Exons during Postnatal Development and Lactation

Prolactin (PRL) has numerous physiological functions that are mediated by its receptors in target cells. Expression of the rat PRL receptor (PRLR) gene is regulated in a tissue-specific manner via the transcriptional activation of five distinct first exons, i.e., E1(1), E1(2), E1(3), E1(4), and E1(5). In the present study, we investigated the expression profiles of these first exon variants of PRLR mRNA in the rat choroid plexus, which is considered to be a site of receptor-mediated PRL transport from the blood to cerebrospinal fluid. Real-time PCR analysis revealed that E1(3)-, E1(4)-, and E1(5)-PRLR mRNA expression levels increased in the choroid plexus in male and female rats during postnatal development, with markedly higher level of E1(4)-PRLR mRNA. In female rats, the E1(4)-PRLR mRNA expression levels increased markedly during lactation compared with the diestrus state, whereas there was no increase in the E1(3)- and E1(5)-PRLR mRNA levels. The E1(4)-PRLR mRNA expression pattern was similar to that of the total PRLR mRNA. The PRL plasma concentration generally correlated with the E1(4)-PRLR mRNA expression levels in both sexes. These findings suggest that PRLR gene expression in the choroid plexus is upregulated mainly via the transcriptional activation of the E1(4)-first exon.

Mammary cell activity and turnover in dairy cows treated with the prolactin-release inhibitor quinagolide and milked once daily

To assess the regulation of mammary cell activity, survival, and proliferation by prolactin (PRL), 5 Holstein cows in early lactation received daily i.m. injections of 1mg of quinagolide, a suppressor of PRL release, for 9 wk, whereas 4 control cows received the vehicle (water) only. During the last week of treatment, one udder half was milked once a day (1×) and the other twice a day (2×). Mammary biopsies were harvested 1 wk before and 4 and 8 wk after the start of quinagolide treatment. The quinagolide injections reduced milk yield and resulted in lower levels of κ-casein and α-lactalbumin mRNA in the mammary biopsies at wk 4 compared with the control cows. In the mammary tissue of the quinagolide-treated cows at wk 8 of treatment, cell proliferation (as determined by proliferating cell nuclear antigen labeling) was lower and apoptosis (as determined by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay) was higher than in the mammary tissue of the control cows. During differential milking, mammary epithelial cells (MEC) were extracted from the milk by centrifugation and purified by immunocytochemical binding to allow variations in the levels of mammary transcripts to be observed. After 9 wk of treatment, levels of α-lactalbumin and κ-casein mRNA were lower in the MEC isolated from milk of the quinagolide-treated cows. This effect was associated with lower PRL receptor mRNA levels and a tendency toward lower viability in the milk-isolated MEC from the 2×-milked glands. The decrease from 2× milking to 1× milking also downregulated α-lactalbumin and κ-casein transcripts in the milk-isolated MEC. Viability was higher for the MEC collected from the 1×-milked udder halves compared with the 2×-milked halves. In conclusion, the reduction in milk yield after chronic administration of the PRL-release inhibitor quinagolide is associated with a reduction in mammary cell activity, survival, and proliferation in lactating dairy cows. Reduced milking frequency was also associated with a decrease in MEC activity.

Differential Changes in Responses of Hypothalamic and Brainstem Neuronal Populations to Prolactin During Lactation in the Mouse

During lactation, there are numerous functional adaptations in the maternal brain. There is evidence that the high levels of circulating prolactin present during lactation might contribute to these adaptive changes. The present study aimed to investigate levels of functional prolactin-mediated signal transduction in the brain of lactating mice, using prolactin-induced phosphorylation of signal transducer and activator of transcription 5 (pSTAT5) as a marker, and compare these to the effect of exogenous prolactin during diestrus. On Day 7 of lactation, widespread induction of pSTAT5 was observed in numerous regions of the mouse forebrain and brainstem. In the medial preoptic nucleus, bed nuclei stria terminalis, paraventricular nucleus, and medial amygdala of the forebrain, and in the rostral periaqueductal gray, parabrachial nucleus, dorsal raphe, and the raphe obscurus nucleus of the brainstem, pSTAT5 expression was markedly increased during lactation compared with the response to exogenous prolactin during diestrus. In the anteroventral periventricular nucleus, arcuate nucleus, ventromedial nucleus, and dorsomedial nucleus, responses in lactation were comparable to diestrus. Conversely, in the area postrema of the brainstem, there was a reduction in response to prolactin, with a loss of pSTAT5 expression, during lactation. These differential responses following either acute or chronic elevations in prolactin were not accompanied by any changes in levels of prolactin receptor mRNA, when measured by in situ hybridization. These data are consistent with the hypothesis that prolactin might mediate widespread adaptive responses in the maternal brain.

Expression Patterns of the Prolactin Receptor Gene in Chicken Lymphoid Tissues During Embryogenesis and Posthatch Period

Prolactin (PRL) is a pituitary hormone with multiple homeostatic roles among vertebrates. Although it has mainly been studied in relation to its role during the initiation and maintenance of incubation behavior in avian species, it has also been shown to act on the immune system. In this study, levels of PRL receptor (PRLR) mRNA were quantified by real-time PCR, and tissue expression was localized by in situ hybridization in primary and secondary lymphoid organs. Prolactin receptor was shown to be expressed in the bursa follicles, thymus lobules, and splenic pulp at all stages of development examined. Levels of PRLR expression were consistently higher in the bursa of Fabricius when compared with other lymphoid organs, suggesting that PRL acts primarily on bursal development. Furthermore, levels of PRLR mRNA appeared to fluctuate during embryogenesis, with a significant increase observed at embryonic day 19 in the bursa, at 7 d of age in the thymus, and on hatching day in the spleen. Thus, PRL might play an important role during the development of the immune system in chickens.

Endocrine systems in juvenile anadromous and landlocked Atlantic salmon ( Salmo salar): Seasonal development and seawater acclimation

The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4 days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11β-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11β-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon.