Osmoregulatory action of PRL,GH, and cortisol in the gilthead seabream (Sparus aurata L)

The osmoregulatory actions of ovine prolactin (oPRL), ovine growth hormone (oGH), and cortisol were tested in the euryhaline gilthead seabream Sparus aurata. Acclimated to sea water (SW, 40 ppt salinity, 1000 mOsm/kg H(2)O) or brackish water (BW, 5 ppt, salinity, 130 mOsm/kg H(2)O), injected every other day for one week (number of injections, 4) with saline (0.9% NaCl), oPRL (4 microg/g body weight), oGH (4 microg/g body weight) or cortisol (5 microg/g body weight), and transferred from SW to BW or from BW to SW 24h after the last injection. Fish were sampled before and 24h after transfer. Gill Na(+), K(+)-ATPase activity, plasma osmolality, plasma ions (sodium and chloride), plasma glucose, and muscle water moisture were examined. SW-adapted fish showed higher gill Na(+), K(+)-ATPase activity, plasma osmolality, and plasma ions levels than BW-adapted fish. Transfer from SW to BW decreased plasma osmolality and ions levels after 24h, while transfer from BW to SW increased these parameters, whereas gill Na(+),K(+)-ATPase activity was unaffected. oPRL treatment significantly decreased gill Na(+),K(+)-ATPase activity and increased plasma osmolality and ions in SW- and BW-adapted fish. This treatment minimizes loss of osmolality and ions in plasma after transfer to BW and increased these values after transfer to SW. No significant changes were observed in gill Na(+),K(+)-ATPase activity, plasma osmolality, and plasma ions in oGH-treated group with respect to saline group before or after transfer from SW to BW or from BW to SW. Treatment with cortisol induced, in SW-adapted fish, a significant increase of gill Na(+),K(+)-ATPase activity and decrease of plasma osmolality and plasma ions. In BW-adapted fish this treatment induced a significant increases in gill Na(+),K(+)-ATPase activity, plasma osmolality, and plasma ions. After transfer to SW cortisol-treated fish had higher plasma osmolality than the saline group. Our results support the osmoregulatory role of PRL in the adaptation to hypoosmotic environment in the gilthead seabream S. aurata. Further studies will be necessary to elucidate the osmoregulatory role of GH in this species. Cortisol results suggest a "dual osmoregulatory role" of this hormone in S. aurata.     

Impact of acute and chronic ethanol exposure on prolactin in both male and female rats

The deleterious effects of ethanol (EtOH) on reproduction have been well documented. This disruption is usually associated with alterations in prolactin (PRL) levels, which is relevant since this hormone is an important participant in the reproductive system. Reported EtOH-induced changes in PRL (i.e., stimulation or inhibition) have varied. These differences may have been owing to the gender or age/sexual maturity of the animal and the mode of the administration of EtOH. Therefore, to clarify the impact of EtOH on PRL, a series of experiments were conducted utilizing rats of both genders, exposed to EtOH acutely or chronically, as adults and as they progressed through puberty. In general, in younger animals of both genders, EtOH depressed serum PRL whether given acutely or chronically. In adult males, acute EtOH actually stimulated PRL levels while chronic administration had no effect. In adult females, EtOH’s effect was highly dependent on the stage of the estrous cycle in which EtOH was given and during which PRL was measured. In conclusion, our studies have shown that the PRL response to EtOH is dependent on the gender and age/sexual maturity of the animals as well as on the mode of administration.     

羊骨胶原肽对青春期大鼠催乳素和促黄体生成素分泌脉冲的影响

目的 研究羊骨胶原肽(sheep bone collagen peptide,SBCP)对类固醇诱导的去卵巢大鼠催乳素(prolactin,PRL)和促黄体生成素(luteinizing hormone,LH)分泌脉冲的影响.方法 6周龄子宫颈未开口的青春期SD大鼠实施双侧卵巢摘除手术,康复1周或3周后以类固醇替代方法诱导PRL和LH脉冲,处理组同时按1000 mg/(kg·d)的剂量以SBCP灌胃,通过颈导管采集血样,利用放射免疫技术测定各组大鼠外周血中的LH和PRL浓度.结果 对于术后康复1周的大鼠,SBCP对LH脉冲振幅起到增强作用,而对PRL脉冲没有影响;对于术后康复3周的大鼠,SBCP对LH和PRL脉冲振幅均表现为降低作用,但卵巢摘除后立即给予SBCP可减弱这种降低作用.结论 雌激素和孕激素替代注射的同时,补充羊骨胶原肽,不仅仍可诱导LH和PRL脉冲的产生,还可预防由于卵巢摘除带来的骨代谢紊乱,免疫力低下等不良影响,因而是对现有类固醇替代方法的改良.     

Prolactin replacement must be continuous and initiated prior to 21 d of age to maintain hypothalamic dopaminergic neurons in hypopituitary mice

The prolactin (PRL) deficit in mice homozygous for the spontaneous Ames dwarf (df) mutation coincides with a marked reduction in the number of PRL-regulating tuberoinfundibular dopaminergic (TIDA) neurons. The TIDA deficit develops after 14–21 d postnatally and may be prevented by PRL replacement initiated at 12, but not at 60, d of age. The present study was designed to define further the developmental period during which PRL can prevent the deficit in the number of TIDA neurons in df/df mice, as well as to evaluate whether exposure to PRL neonatally affects the response to PRL by TIDA neurons in later development. To address the first aim, litters of df/df and normal (DF/df) mice were treated daily with ovine PRL (50 μg intraperitoneally), starting at 12, 21, or 30 d of age. To address the second aim, DF/df and df/df animals treated with PRL for 30 d starting at 12 d of age were subjected to PRL withdrawal (15 d of saline vehicle treatment), followed by PRL retreatment. All brains were evaluated using both catecholamine histofluorescence and tyrosine hydroxylase (TH) immunocytochemistry. Total numbers of TH-immunostained cells were counted in area A12 (TIDA neurons) and in A13 (medial zona incerta). Qualitatively, catecholamine fluorescence in A12 perikarya and terminals in df/df mice was enhanced by PRL treatment initiated at 12 or 21, but not at 30, d of age. TH immunostaining intensity was enhanced in all df/df PRL-treated groups, compared with saline treatment. However, total numbers of TH-positive TIDA neurons were reduced significantly in df/df mice treated with PRL beginning at 21 or 30 d, as well as with saline at 12 d, compared with similarly treated DF/df groups and with df/df animals treated with PRL beginning at 12 d (p<0.01 for all comparisons). Among dwarf mice treated with PRL beginning at 12 d, followed by PRL withdrawal, the numbers of TH-positive TIDA neurons were greater than those of saline-treated dwarfs, but less than those in DF/df mice (p<0.05 for both comparisons). In dwarfs retreated with PRL after withdrawal, the TIDA population was also smaller than that in normal animals (p<0.05), although it was larger than in vehicle-treated dwarfs of the same age (p<0.05). No effect of PRL treatment on TIDA cell numbers in normal mice, or of treatment or mouse phenotype on the number of TH-positive cells in zona incerta, occurred in either experiment. These results indicate that the effect of PRL on preventing the reduction in the TIDA population in df/df mice is limited to a developmental period prior to 21 d postnatally. In addition, this study provides evidence that continuous PRL feedback is required to maintain normal numbers of TIDA neurons. These findings extend the evidence for a critical role of PRL feedback in the differentiation and preservation of phenotype in TIDA neurons.     

Circulating prolactin and corticosterone concentrations during the development of migratory condition in the Dark-eyed Junco, Junco hyemalis

Endogenous plasma prolactin and baseline corticosterone concentrations were measured in Dark-eyed Juncos (Junco hyemalis, n=27) photostimulated into migratory condition to look at how these hormones may be linked to the development of migratory condition. In addition to the commonly used assay for corticosterone, a recombinant-derived European starling prolactin assay validated for Dark-eyed juncos was used to measure endogenous prolactin in order to detect small but significant changes in plasma prolactin levels. In response to transfer from short (10.5L:13.5D) to long (18L:6D) days, the birds increased in body mass, fat score, daily food intake, and nocturnal migratory locomotor activity (Zugunruhe). On short-days, both hormones were low (corticosterone mean=2.89ng/mL+/-0.48 SE; prolactin mean=6.43ng/mL+/-1.31 SE). But, within 14 days of photostimulation both hormones increased significantly (Day 14: corticosterone mean=5.71ng/mL+/-0.77 SE; prolactin mean=19.67ng/mL+/-2.81 SE), rising further by Day 48 (corticosterone mean=8.41ng/mL+/-0.72; prolactin mean=112.67ng/mL+/-9.18 SE). On Day 48, birds with the most fat (fat score=3) had significantly higher corticosterone levels than those with less fat (fat score=2). This pattern, albeit not statistically significant, was similar for prolactin. These results illustrate that, independent of the seasonal peak in prolactin associated with the onset of photorefractoriness, plasma prolactin levels can rise, in concert with corticosterone, as birds come into spring migratory condition, providing some support for earlier hypotheses that these two hormones play an integral role in the development of migratory condition. Whether similar changes in plasma prolactin occur with respect to autumn migration, as does baseline corticosterone, has yet to be determined.     

Prolactin regulates mammary epithelial cell proliferation via autocrine/paracrine mechanism

Prolactin (PRL) is essential for a number of developmental events in the mammary gland. Work with PRL and PRL receptor knockout mice has shown that PRL indirectly regulates ductal side branching during puberty and directly controls lobuloalveolar development and lactogenesis during pregnancy. Anterior pituitary or placental PRL is thought to be responsible for these functions via an endocrine mechanism; however, PRL is also produced in a number of extrapituitary sites including the mammary gland. The physiologic relevance of mammary PRL remains unknown. In this study we utilized mammary recombination in Rag1^−/− hosts, to determine whether mammary PRL plays a role in the regulation of mammary gland development. Mammary glands formed with the PRL gene deleted from either the epithelium, stroma, or both displayed normal development, on the basis of whole mount and hematoxylin and eosin histology, during puberty and lactation. At the end of pregnancy, a 2.8-fold decrease in bromodeoxyuridine incorporation was observed in the epithelial cells of mammary glands formed using PRL knockout epithelium compared with those formed using wildtype epithelium. No balancing alteration in the rates of apoptosis was detected. Thus, mammary-derived PRL influences mammary epithelial cell proliferation via an autocrine/paracrine mechanism, establishing a physiologic function for mammary PRL during mammopoiesis.     

光激化学发光技术定量检测血清PRL方法的建立及评价

摘要：目的 基于光激化学发光技术平台初步建立血清催乳素（PRL）的分析方法,并评估其性能指标。方法 将发光纳米微球和生物素分别标记于一对人PRL单抗,两者与血清中待检泌乳素、链霉亲和素标记的感光微球（通用感光溶液）在均相条件下形成双抗体夹心的检测体系,并对该检测体系的性能指标和相关性进行评价。结果 本方法的批内及批间精密度（变异系数）分别为4.60%和5.25%;检测范围为2.48~ 4240 μIU/ml;加标回收试验的回收率在96.25%-97.16%;胆红素<20 mg/dL、血红蛋白<200 mg/dL、甘油三酯<3000 mg/dL时,均无干扰现象发生;且该方法与贝克曼Unicel Dxi 800 Access 2酶促化学发光免疫系统分析法具有良好的相关性。 结论 光激化学发光法检测血清PRL的方法具有良好的分析性能,可满足临床诊断需求。     

Activation of the growth hormone/insulin-like growth factor axis by treatment with 17 alpha-methyltestosterone and seawater rearing in the tilapia,Oreochromis mossambicus

Effects of 17 alpha-methyltestosterone (MT) treatment and environmental salinity on the growth hormone (GH)/insulin-like growth factor (IGF) axis were examined in the euryhaline tilapia, Oreochromis mossambicus. Yolk-sac fry were collected from brood stock in fresh water (FW). After yolk-sac absorption, they were assigned randomly to 1 of 4 groups: FW, MT treatment in FW, SW, and MT treatment in seawater (SW). After 147 days, FW controls had the lowest levels of GH mRNA followed by FW fish treated with MT and SW control fish. Seawater fish fed with a diet containing MT, which grew the fastest, had significantly higher levels of GH mRNA than all the other groups. A significant correlation was observed between GH mRNA and the size of the individual fish. By contrast, plasma GH levels did not vary significantly among the groups. Pituitary GH mRNA levels, plasma IGF-I levels, and fish size varied in a correlated pattern, i.e., SW+MT>FW+MT=SW control>FW control. The tilapia pituitary produces two prolactins (PRLs), PRL(177) and PRL(188). Prolactin(177), but not PRL(188), exhibits growth-promoting actions in FW tilapia. Pituitary mRNA levels of both PRLs were significantly higher in fish reared in FW than those reared in SW. Treatment with MT significantly increased mRNA levels of both PRLs in FW, but had no effect on SW fish. No correlation was seen between plasma PRL levels and growth or between PRL mRNA levels and growth. These results indicate that SW rearing and MT treatment stimulate the GH/IGF-I axis, and suggest that pituitary GH mRNA at this stage of development is a better indicator of growth than plasma levels of GH and IGF-I.     

Preoperative assessment for pituitary surgery

Evaluation of pituitary function is essential before pituitary surgery. In hyperprolactinaemic patients with a pituitary macrolesion, tumoral secretion of prolactin must be distinguished from ‘disconnection’ hyperprolactinaemia; serum prolactin >200 mcg/l is virtually diagnostic of a macroprolactinoma whereas levels <80 mcg/l usually indicate ‘disconnection’. The prolactin ‘hook effect’ should be excluded. A minimum set of pre-operative endocrine tests should include serum electrolytes, cortisol (at 08.00–09.00 h), free-T4, TSH, prolactin, oestradiol/testosterone, LH, FSH and IGF-1. Some clinicians will choose to perform pre-operative Synacthen or insulin tolerance testing to further define ACTH reserve. If basal cortisol, Synacthen or insulin tolerance test results are abnormal, steroid supplementation is indicated for at least the first 48 h after surgery. If pre-operative basal cortisol is <100 nmol/l, replacement steroids should be continued until the time of post-operative pituitary function testing (6–8 weeks after surgery). In patients with pre-operative basal cortisol >450 nmol/l, peri-operative glucocorticoid replacement is unnecessary and further cortisol levels should be checked a few days after surgery. Most clinicians defer detailed evaluation of growth hormone reserve until after surgery. Diabetes insipidus is rarely a problem before surgery in patients with pituitary adenomas but may occur post-operatively. Close co-operation between anesthetic, endocrine and surgical teams is strongly recommended.