垂体瘤转化基因在大鼠垂体泌乳素腺瘤中基因表达的研究

目的研究垂体瘤转化基因在实验大鼠垂体腺瘤组织中的表达规律,探讨垂体瘤转化基因在垂体腺瘤形成过程中的作用。方法实验用雌性Wistar大鼠40只,摘除双侧卵巢,将大鼠完全随机分为实验组和对照组。通过腹腔注射苯甲酸雌二醇建立大鼠垂体腺瘤模型,分别对实验组和对照组大鼠垂体组织中垂体瘤转化基因进行定性和半定量分析,应用SPSS11．5统计软件对资料处理分析。结果实验组大鼠垂体质量为（52．35±4．97）mg,大约为对照组垂体质量（12．02±0．77）mg的4倍,差异有统计学意义（t=29．98,P=0．000）。实验组大鼠血清泌乳素浓度[（198．23±93．07）ng／L]大约是对照组血清泌乳素浓度[（50．12±14．24）ng／L]的4倍,差异有统计学意义（t=7．035,P=0．000）。对垂体瘤转化基因表达进行半定量分析,结果对照组为（0．24±0．08）,实验组为（1．41±0．13）。结论雌激素诱导大鼠可以形成垂体泌乳素腺瘤;垂体瘤转化基因参与调节雌激素诱导的大鼠垂体腺瘤形成。     

Haloperidol treatments increased macrophage activity in male and female rats: influence of corticosterone and prolactin serum levels.

Haloperidol is a receptor D2 antagonist frequently used in the treatment of schizophrenic patients. Haloperidol increased prolactin release from anterior pituitary gland, and prolactin modulates immune system activity. Groups of six male and female rats received an acute 2 mg/kg haloperidol treatment (E1), or a long-term (E2) haloperidol treatments (2 mg/kg/day for 21 days); control rats were treated similarly, but with control solution (groups C1 and C2, respectively). In this work long-term haloperidol treatment (E2) increased macrophage spreading, phagocytosis and NO release in male and female rats. However, acute haloperidol treatment (E1) did not change macrophage activity. Corticosterone and prolactin serum levels were increased after acute (E1) and long-term (E2) haloperidol treatments in male and female rats, being this increment higher in female. Macrophage of male and female rats presented the same pattern of alterations after acute and long-term haloperidol treatments. Haloperidol-induced macrophage activation was discussed in the light of a possible indirect effect through prolactin increments in rats, or, alternatively, as a consequence of a direct action of macrophage dopamine receptor.     

Habituation to repeated stress is stressor specific

Rats were exposed to 15 min of restraint or footshock or forced running in an activity wheel once a day for 10 days. Control groups were handled only. On the 11th day, rats from each stressor group and controls were exposed to 15 min of one stressor in a crossed design such that all combinations of one chronic stressor and one acute stressor were performed. Rats were sacrificed immediately following removal from their home cage or after 15 min stressor exposure on the 11th day and plasma corticosterone and prolactin and pituitary cyclic AMP levels were determined. There were no measured differences in these stress indices among groups of rats sacrificed immediately upon removal from their home cage on day 11 regardless of previous history on days 1 through 10. Plasma corticosterone and plasma prolactin and pituitary cyclic AMP levels were elevated in all rats exposed to any of the three stressors immediately prior to sacrifice as compared to all rats not exposed to stress immediately before sacrifice. However, plasma prolactin and pituitary cyclic AMP responses to each of the 3 stressors were attenuated in rats which had previous exposure to that specific stressor as compared to rats which had previous experience with a different or no stressor. We conclude that habituation results from behavioral experience with a particular stressor rather than biochemical adaptation resulting from repeated challenge to hormonal and neurochemical systems responsive to stress.     

Biochemical indices of reactivity and habituation in rats with hippocampal lesions

The response of rats with hippocampal lesions to acute and repeated footshock stress was assessed by measurement of pituitary cyclic AMP, plasma corticosterone and plasma prolactin. Levels of pituitary cyclic AMP and plasma prolactin and corticosterone were similar in never-shocked sham controls, and never-shocked hippocampal and neocortical lesion groups. Acute first time shock markedly elevated all measured stress indices with no statistically significant differences observed among surgical groups. In rats subjected to repeated stress (one 15 min footshock session per day for 10 days) and sacrificed 24 hours after the last shock session, levels of pituitary cyclic AMP and plasma hormones were similar to levels in never-shocked shams with the exception of the hippocampal animals. The rats with hippocampal lesions had higher levels of pituitary cyclic AMP, plasma corticosterone and plasma prolactin compared to never-shocked animals. We suggest that these data reflect a hyperreactive response of the hippocampal animals to a situation previously associated with shock. Finally, rats in all surgical groups subjected to repeated stress and sacrificed immediately after the last shock session showed a diminished cyclic AMP response to the stressor as compared to first footshock session response, demonstrating a habituation to the stressor as measured by this index. No differences in habituation were observed among hippocampal, neocortical and sham groups. Plasma hormone responses did not habituate in any group. These data support the behavioral observations of hyperreactivity in hippocampal animals and indicate that hippocampal animals are able to habituate to repeated stressful stimuli.     

Adrenocorticotropin (ACTH) and corticosterone secretion by perifused pituitary and adrenal glands from rodents exposed to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD)

Although in utero maternal stress has been shown to have lasting effects on rodent offspring, fetal effects of chemically-induced alterations of the maternal hypothalamic-pituitary-adrenal axis (HPA) have not been well studied. This study examined the effects of in vivo 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on pituitary-adrenal function in the male rat, pregnant female rat and pregnant female mouse. The secretion of adrenocorticotropin (ACTH) and corticosterone (CORT) in pituitary and adrenal glands, respectively, was assessed in ex vivo perifusion cultures. Male and pregnant female (gestation day 8) Sprague-Dawley rats were gavaged once with 10 microgram/kg TCDD, pregnant female mice once with 24 microgram/kg TCDD, and euthanized 10 days later. Hemi-pituitary (rat) or whole anterior pituitaries (mice) and right adrenal glands from the same animal were quartered, perifused under baseline and stimulated conditions. In both males and pregnant females, TCDD did not affect corticotropin releasing hormone (CRH)-stimulated ACTH secretion. Neither total pituitary ACTH nor plasma ACTH was altered in either sex or species by TCDD treatment. ACTH-stimulated CORT secretion was not affected by TCDD in either sex or species, and adrenal tissue and plasma CORT levels were unchanged in males and pregnant females by TCDD. However, the plasma ACTH:CORT ratio was decreased about 46% in male rats treated with TCDD. Plasma CORT levels were 23-fold higher and plasma ACTH levels were 1.5-fold higher in pregnant females than in male rats. In male versus female rats, adrenal CORT and anterior pituitary ACTH tissue levels were about 7.5- and 1.75-fold higher and ACTH, respectively. Female mouse adrenal tissue CORT was about 4-fold greater than female rat. The reduced plasma ACTH:CORT ratio in the male rat suggests that TCDD disturbs HPA function. Exposure of male rat to a 5-fold higher dose in earlier studies clearly demonstrated effects of TCDD on male rat HPA. The present study identified substantial HPA performance differences between male and pregnant female rats. The failure to detect a response to TCDD in pregnant female rat and mouse could be a function of both TCDD dose and the high level of secretion of both ACTH and CORT in pregnant animals. For the rat or mouse, a single exposure to TCDD during pregnancy does not appear sufficient to induce maternally-mediated developmental, reproductive and behavioral toxicity via the HPA axis.     

Decrease of prolactin secretion via stimulation of pituitary dopamine D-2 receptors after application of talipexole and SND 919

The present experiments were performed to investigate the effects of talipexole (B-HT 920) and SND 919 on prolactin release from the anterior pituitary glands of rats both in vivo and in vitro. The basal serum prolactin levels were reduced dose dependently by s.c. administration of talipexole or SND 919 at doses of 5-100 micrograms/kg. Daily treatment with estradiol (35 micrograms/kg for 3 days) increased serum prolactin levels in male rats to levels 4-fold higher than those of non-primed rats. This increase was suppressed by administration of talipexole or SND 919. In vitro, the spontaneous prolactin release into perfusates from isolated anterior pituitary was inhibited by talipexole or SND 919 added at concentrations ranging from 10(-9) to 10(-6) M. This inhibitory effect of SND 919 was blocked by concurrent application of a dopamine D-2 receptor antagonist, YM-09151-2. The spontaneous prolactin release from the anterior pituitary isolated from estradiol-primed rats was 2-fold higher than that from non-primed rats. This increased release was also inhibited by application of either drug. The inhibitory effects of these drugs were greater in estradiol-primed rats than in non-primed rats when expressed as percent inhibition of control prolactin release. The results suggest that talipexole and SND 919 have a selective dopamine D-2 receptor agonistic property and are almost completely effective to counteract the enhancement of prolactin release induced by estrogens via stimulation of dopamine D-2 receptors in the anterior pituitary.     

Failure of chronic haloperidol to affect prolactin secretion due to acute haloperidol administration

Withdrawal from chronic haloperidol exposure was associated to unaltered circulating levels of prolactin (PRL), decreased 3H-spiperone binding sites in the anterior pituitary and increased 3H-spiperone binding sites in the striatum of male rats. Haloperidol (0.1 mg/kg ip) induced similar rises in plasma PRL in haloperidol-or saline-treated rats and the dose of 0.01 mg/kg was ineffective in both groups. These findings illustrate the poor relatedness existing at the pituitary D2 receptor between biochemical and functional indices.     

Effect of GABA-T inhibitors on prolactin secretion in vitro

A study was made of the effect of GABA-transaminase (GABA-T) inhibitors on the in vitro release of prolactin by pituitaries of male and female rats. Aminooxyacetic acid (AOAA) and gamma-acetylenic GABA (GAG) added to the incubation medium decreased prolactin release from both male and female rat pituitaries. Additive effects on prolactin release were only observed when male rat pituitaries were incubated with AOAA plus GABA. Prolactin concentration in the pituitary gland was also decreased by AOAA in both sexes. The present results lend support to the idea of an inhibitory action of GABA on prolactin release by the pituitary gland.     

Absence of D1 dopamine receptors that stimulate prolactin release in the rat pituitary

It has been shown recently that SKF 38393-A (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine-7-ol), a D-1 receptor agonist, possesses a prolactin-releasing effect in the rat, though the pituitary or central nervous system location of the receptors involved has not been clarified. The aim of our study was to elucidate this point. SKF 38393-A administered to freely moving adult female and male rats induced a striking, short-lived increase of basal prolactin levels. The prolactin stimulatory effect of SKF 38393-A was counteracted by pretreatment with SCH 23390, A D-1 receptor blocker. SKF 38393-A (10(-11)-10(-6)M) added to monolayer primary cultures of anterior pituitary cells from rats of both sexes failed to modify prolactin release. At higher concentrations (10(-5)-10(-4) M) the drug induced a slight inhibition of prolactin release. Similarly, SKF 38393-A failed to stimulate adenylate cyclase activity in anterior pituitary membranes from rats of both sexes at low concentrations, while it inhibited enzyme activity at higher concentrations (10(-5)-10(-3) M). The latter effect was counteracted by concomitant addition of the antagonist of D-2 receptors, 1-sulpiride. These data demonstrate that: (1) the anterior pituitary does not contain D-1-dopamine receptors (positively coupled to adenylate cyclase) stimulatory to prolactin release; (2) the striking prolactin-releasing effect of SKF 38393-A in the rat is due to activation of extra-pituitary D-1 dopamine receptors; (3) SKF 38393-A, at high concentrations, is capable of activating pituitary D-2 receptors.     

Females do not express learned helplessness like males do.

Women are more likely than men to suffer from stress-related mental disorders, such as depression. In the present experiments, we identified sex differences in one of the most common animal models of depression, that of learned helplessness. Male and female rats were trained to escape a mild footshock each day for 7 days (controllable stress). Each rat was yoked to another rat that could not escape (uncontrollable stress), but was exposed to the same amount of shock. One day later, all stressed rats and unstressed controls were tested on a more difficult escape task in a different context. Most males exposed to uncontrollable stress did not learn to escape and were therefore helpless. In contrast, most females did learn to escape on the more difficult escape task, irrespective of whether they had been exposed to controllable or uncontrollable stress. The sex differences in helplessness behavior were not dependent on the presence of sex hormones in adulthood, because neither ovariectomy of females nor castration of males abolished them. The absence of helplessness in females was neither dependent on organizational effects of testosterone during the day of birth, because masculinized females did not express helplessness as adults. Thus, sex differences in helplessness behavior are independent of gonadal hormones in adulthood and testosterone exposure during perinatal development. Learned helplessness may not constitute a valid model for depressive behavior in women, at least as reflected by the response of female rats to operant conditioning procedures after stressful experience.     

Inhibition by naloxone of the rise in hypothalamic dopamine and serum prolactin induced by ethanol

We investigated the effect of naloxone on the concentration of dopamine in the hypothalamus and on the concentration of prolactin in serum and anterior pituitary of male rats acutely treated with ethanol. Acute ethanol administration increased serum prolactin levels and hypothalamic dopamine concentration. Pituitary prolactin was not modified by this treatment. Naloxone administered 15 min before the animals were sacrificed decreased serum prolactin levels and hypothalamic dopamine concentration in ethanol-treated rats. These results suggest that ethanol increases prolactin secretion because it decreases the release of dopamine by the hypothalamus. Naloxone decreases prolactin release probably because it antagonizes the inhibitory action of opioids on dopaminergic neurons.     

回乳抑增方抗泌乳素腺瘤的药效及作用机制研究

目的：研究中药复方回乳抑增方抗泌乳素腺瘤的药效及作用机制。方法：建立SD雌性大鼠泌乳素腺瘤模型,大鼠随机分为7组,分别为正常组、模型组各14只,手术对照组、溴隐亭阳性药组、回乳抑增方高剂量组、回乳抑增方中剂量组、回乳抑增方低剂量组各6只。除正常组和手术对照组外,其他5组模型大鼠灌胃给予相应药物30 d,每天1次。应用基因芯片筛选正常组大鼠和泌乳素腺瘤模型组大鼠垂体组织基因间的差异。运用Western Blot测定各组大鼠垂体组织中泌乳素（PRL）、胞内磷脂酰肌醇激酶（PI3K）、蛋白激酶B（AKT）和哺乳动物雷帕霉素靶蛋白（mTOR）蛋白含量。结果：大鼠泌乳素腺瘤模型建立成功。与正常组相比,模型组大鼠垂体组织的PI3K基因表达显著。与正常组相比,模型组大鼠垂体组织中PRL、PI3K、AKT和mTOR表达显著升高（^**P<0.01）,而与模型组相比,高、中和低剂量的回乳抑增方给药组大鼠垂体组织中PRL、PI3K、AKT和mTOR表达显著降低（^##P<0.01）。结论：回乳抑增方可显著抑制泌乳素腺瘤的增长和泌乳素的过度分泌,作用机制与调控PI3K/AKT/mTOR信号通路有关。     

The effect of 2-Br-α-ergocryptine on the hepatic steroid metabolism and serum pituitary hormone levels in normal rats and rats with an ectopic pituitary

The effect of a dopaminergic agonist, CB-154 (2-Br-α-ergocryptine), on the hepatic steroid metabolism in normal male and female rats, and in hypophysectomized male animals bearing an implanted pituitary under the kidney capsule, has been investigated. The serum levels of the four pituitary hormones LH, FSH, prolactin and growth hormone, were also measured. In normal animals, CB-154 reduced the serum level of prolactin without significantly affecting levels of LH, FSH or growth hormone and without masculinizing hepatic steroid metabolism of female rats of feminizing hepatic steroid metabolism of male rats. Implantation of a pituitary gland from age-matched female rats in hypophysectomized male rats caused an increase in prolactin and growth hormone levels in serum and a shift towards a more feminine type of steroid metabolism. Treatment with CB-154 reduced the prolactin level without affecting LH, FSH or growth hormone levels and without masculinizing hepatic steroid metabolism. In conclusion, the drug, CB-154, causes a marked and selective decrease in circulating prolactin levels without affecting the sex differentiation of hepatic steroid metabolism thus indicating that these two parameters are not related. A certain correlation between growth hormone levels and degree of femininity of steroid metabolism was seen but the significance of this is debatable.     

Estrogen-like activity of chlordecone (Kepone) on the hypothalamo-pituitary axis: Effects on the pituitary enkephalin system

Similarities between the activity of chlordecone and estrogen on the hypothalamo-pituitary axis (HPA) were examined by using the pituitary enkephalin system as a model. A single injection (25 to 75 mg/kg, ip) or repeated injections (2.5 to 10 mg/kg/day for 10 days, ip) of chlordecone caused a time- and dose-related decrease in pituitary [Met⁵]-enkephalin-like immunoreactivity (ME-LI) in adult rats. Similar to the reported effects of estrogen, chlordecone treatment decreased the levels of ME-LI in the anterior lobe but not in the neurointermediate lobe of male pituitaries. Furthermore, chlordecone failed to alter the pituitary levels of ME-LI in female rats. The level of another pituitary peptide hormone, β-endorphin, was increased in male rats after chlordecone treatment, indicating some degree of selectivity of this effect. Similarities between chlordecone and estrogen were found with other pituitary hormones, i.e., implantation of diethylstilbestrol or of chlordecone in ovariectomized rats caused qualitatively similar changes in serum prolactin and luteinizing hormone levels. These results suggest that chlordecone qualitatively resembles estrogen in its effect on some HPA peptide systems.     

Chromium VI administration induces oxidative stress in hypothalamus and anterior pituitary gland from male rats

Hexavalent chromium (Cr VI)-containing compounds are known carcinogens which are present in industrial settings and in the environment. The major route of chromium exposure for the general population is oral intake. Previously we have observed that Cr VI affects anterior pituitary secretion and causes oxidative stress in vitro. The aim of the present work was to investigate if in vivo Cr VI treatment (100 ppm of Cr VI in drinking water for up 30 days) causes oxidative stress in hypothalamus and anterior pituitary gland from male rats. This treatment produced a 4-fold increase of chromium content in hypothalamus and 10-fold increase in anterior pituitary gland. Lipid peroxidation showed a significant increase in hypothalamus and anterior pituitary. Cr VI augmented superoxide dismutase activity in anterior pituitary gland and glutathione reductase activity in hypothalamus, but glutathione peroxidase and catalase activities remained unchanged in both tissues. Heme oxygenase-1 mRNA expression significantly rose in both tissues. Metallothionein 1 mRNA content increased in anterior pituitary and metallothionein 3 mRNA increased in hypothalamus. These results show, for the first time, that oral chronic administration of Cr VI produces oxidative stress on the hypothalamus and anterior pituitary gland which may affect normal endocrine function.     

Endosulfan effects on pituitary hormone and both nitrosative and oxidative stress in pubertal male rats

The present study was undertaken to investigate in pubertal male rats possible effects of endosulfan administered throughout lactation and gestation on: (a) pituitary gene expression of prolactin, luteinizing hormone (LH), growth hormone (GH) and thyroid stimulating hormone (TSH); (b) circulating levels of these hormones; and (c) expression of nitric oxide synthase 1 and 2 (NOS1 and NOS2), and heme oxygenase-1 (HO-1) at pituitary level. Endosulfan was administered orally at the doses of 0.61 mg/kg/day or 6.12 mg/kg/day, and possible toxic effects were studied in pubertal male pups (at postnatal day 30). Gene expression was evaluated by RT-PCR and plasma hormone levels by RIA. Exposure to both administered doses down-regulated LH, GH and TSH. Treatment with 0.61 mg endosulfan/kg/day decreased prolactin expression, although its plasmatic concentration was decreased by both administered doses. LH secretion was stimulated by both doses, whereas the highest dose increased GH levels and decreased plasma TSH concentration. Endosulfan up-regulated NOS1 and NOS2. We can conclude that in pubertal male rat, prenatal and lactational exposure to endosulfan modifies expression and release of prolactin, LH, GH and TSH, and pituitary NOS1 and NOS2 mRNA levels, suggesting that nitrosative stress can be implicated in the endocrine toxicity of endosulfan at pituitary level.     

Relation between dopaminergic control of pituitary lactotroph function and deceleration of age-related changes in serum prolactin of diet-restricted rats

Pituitary lactotroph function has been examined in diet-restricted (6 hr/day) male and female rats and compared with that in animals fed ad lib. After 12 months the age-related increase in serum prolactin concentration was significantly attenuated in diet-restricted female rats. Similar effects were not observed in male rats. Isolated superfused anterior pituitary glands removed from rats on both feeding regimens at 12 or 18 months and challenged with dopamine in vitro (5 microM) did not show differential prolactin secretion. No significant differences were observed in serum prolactin secretion in vivo after administration of bromocriptine (3 mg/kg body weight, sc) or haloperidol (1.75 mg/kg body weight, ip). These results do not support an altered dopamine receptor function in the anterior pituitary lactotrophs. In contrast, central dopamine receptor function in rats 12 months of age was altered by dietary restriction, since the frequency of cataleptic responses to haloperidol injection (2 mg/kg body weight, ip) was significantly depressed in the test animals.     

Cadmium exposure disrupts GABA and taurine regulation of prolactin secretion in adult male rats

This work was undertaken to evaluate the possible effects of cadmium exposure on 24 h changes of gamma-aminobutyric acid (GABA) and taurine median eminence and pituitary contents. Also the possible alterations of the regulatory mechanisms of GABA and taurine on prolactin secretion were evaluated. Adult male rats were given cadmium at a dose of 25 mg/l of cadmium chloride in the drinking water for 30 days. Control age-matched rats received cadmium free water. Metal exposure induced the appearance of a maximal value of prolactin at 08:00 h. In median eminence, cadmium abolished the GABA and taurine maximal values and decreased GABA and taurine mean levels. In the anterior pituitary, cadmium treatment phase advanced 12 h the peak observed in controls at 00:00 h for both amino acids. There was a positive correlation between GABA and taurine contents in median eminence and the anterior pituitary in both control and cadmium-exposed animals. However, the correlation between GABA or/and taurine with prolactin levels disappeared in cadmium-exposed animals. These results suggest that cadmium exposure affects GABA and taurine daily pattern in the median eminence and anterior pituitary, and those changes explain, at least in part, the modification in the regulatory pattern of prolactin secretion.     

Comparison of the effects of remoxipride and raclopride on nigrostriatal and mesolimbic dopaminergic neuronal activity and on the secretion of prolactin and alpha-melanocyte-stimulating hormone.

Raclopride and remoxipride, which are reported to be selective dopamine-D2 antagonists, are currently under clinical investigation as antipsychotic drugs. The present study compared the relative abilities of these two drugs to alter the activity of nigrostriatal and mesolimbic dopaminergic neurons, and plasma levels of hormones originating from the anterior and intermediate lobes of the pituitary in male rats. Although raclopride was consistently more potent than remoxipride, both drugs produced dose- and time-related increases in concentrations of 3,4-dihydroxyphenylacetic acid in the striatum and nucleus accumbens, which contain terminals of nigrostriatal and mesolimbic dopaminergic neurons, respectively. Both drugs also caused significant dose- and time-related increases in plasma levels of prolactin, but only raclopride increased plasma levels of alpha-melanocyte-stimulating hormone (alpha-MSH). These results suggest that although raclopride and remoxipride are both classified as D2 receptor antagonists they can be distinguished from one another by their relative ability to block the inhibitory dopaminergic control of alpha-MSH from melanotrophs in the intermediate lobe of the rat pituitary.     

Evidence for a direct anterior pituitary site of delta-9-tetrahydrocannabinol action.

The effects of delta-9-tetrahydrocannabinol (THC), alone and in the presence of estradiol (E), on several estrogen-sensitive parameters in the immature female rat were examined, and it was demonstrated that THC administration antagonized the stimulatory effects of E on anterior pituitary weight and on both the secretion and pituitary content of prolactin. In the current study, the anterior pituitary gland was examined as a potential site of THC action in the ability of this cannabinoid to antagonize E-induced stimulation of pituitary function. A stimulatory dose of E (1 nM) significantly elevated prolactin levels in pituitary cells derived from either immature or retired breeder animals. Whereas THC (1 microM) alone had no effect on prolactin levels when compared to controls, THC completely prevented the E-induced increase in media prolactin levels. Moreover, THC blocked the ability of E to desensitize pituitary cells to the inhibitory influence of dopamine. Together with the findings that THC inhibited E-induced stimulation of total RNA synthesis in pituitary cell cultures, these data strongly suggest that THC antagonizes the stimulatory effect of E on the pituitary by a direct action at the adenohypophyseal level.