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.     

Prolactin-releasing peptide and its homolog RFRP-1 act in hypothalamus but not in anterior pituitary gland to stimulate stress hormone secretion

The RF-amide peptides (RFRPs), including prolactin (PRL)-releasing peptide-31 (PrRP-31) and RFRP-1, have been reported to stimulate stress hormone secretion by either direct pituitary or indirect hypothalamic actions. We examined the possible direct effects of these peptides on PRL and adrenocorticotropin (adrenocorticotropic hormone [ACTH]) release from dispersed anterior pituitary cells in culture and on PRL and ACTH secretion following intracerebroventricular (icv) administration in vivo. Neither peptide significantly altered PRL or ACTH release from cultured pituitary cells (male rat donors). Central administration of 1.0 and 3.0 nmol of PrRP-31, but only the higher dose of RFRP-1, significantly elevated serum corticosterone levels in conscious male rats. The effect of PrRP-31 was not blocked by pretreatment (iv) with the corticotropin-releasing hormone (CRH) antagonist, α-helical CRH 9–41; however, pretreatment of the animals (iv) with an antiserum to CRH significantly lowered the hypothalamic-pituitary-adrenal axis response to central administration of PrRP-31. On the other hand, the release of PRL was significantly elevated by 3.0 nmol of RFRP-1, but not PrRP-31, in similarly treated, conscious male rats. Pretreatment with the catecholamine synthesis inhibitor, α-methyl-para-tyrosine, prevented the stimulation of PRL secretion observed following central administration of RFRP-1. RFRP-1 similarly did not alter PRL secretion in rats pretreated with the dopamine, D₂ receptor blocker, domperidone. These results suggest that the RF-amide peptides are not true neuroendocrine regulators of stress hormone secretion in the rat but, instead, act centrally to alter the release of neuroendocrine factors that do act in the pituitary gland to control PRL and ACTH release. In the case of RFRP-1, stimulation of PRL secretion is potentially owing to an action of the peptide to inhibit dopamine release into the median eminence. The corticosterone secretion observed following central administration of PrRP-31 does not appear, based on our current results, to be solely owing to an action of the peptide on CRH-producing neurons but, instead, may be a result of the ability of PrRP-31 to increase as well the exposure of the corticotrophs in vivo to other ACTH secretagogues, such as oxytocin or vasopressin.     

Hormone release is tied to changes in cell size in the osmoreceptive prolactin cell of a euryhaline teleost fish, the tilapia, Oreochromis mossambicus

Prolactin (PRL) cells from a teleost fish, the tilapia, Oreochromis mossambicus, facilitate the direct study of osmoreception. The release of two prolactins, PRL(188) and PRL(177), which act in freshwater osmoregulation in teleost fish, rises in vitro within 5 min after extracellular osmolality falls. An increase in cell size accompanied this rise. Cell size and PRL release also increased, albeit more slowly, following the partial replacement of medium NaCl (55 mOsmolal) with an equivalent concentration of urea, a membrane-permeant molecule. Similar replacement using mannitol, which is membrane-impermeant, elicits no response. These findings suggest that osmoreception is linked to changes in cell volume rather than to extracellular osmolality per se.     

TIDAL WAVES: Network mechanisms in the neuroendocrine control of prolactin release

Neuroendocrine tuberoinfundibular dopamine (TIDA) neurons tonically inhibit pituitary release of the hormone, prolactin. Through the powerful actions of prolactin in promoting lactation and maternal behaviour while suppressing sexual drive and fertility, TIDA neurons play a key role in reproduction. We summarize insights from recent in vitro studies into the membrane properties and network behaviour of TIDA neurons including the observations that TIDA neurons exhibit a robust oscillation that is synchronized between cells and depends on intact gap junction communication. Comparisons are made with phasic firing patterns in other neuronal populations. Modulators involved in the control of lactation – including serotonin, thyrotropin-releasing hormone and prolactin itself – have been shown to change the electrical behaviour of TIDA cells. We propose that TIDA discharge mode may play a central role in tuning the amount of dopamine delivered to the pituitary and hence circulating prolactin concentrations in different reproductive states and pathological conditions.     

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。     

剖宫产术后罗哌卡因复合吗啡硬膜外镇痛对泌乳素的影响

目的观察剖宫产术后病人硬膜外连续注射罗哌卡因与吗啡对泌乳素的影响。方法60例健康足月初产妇,择期在联合椎管内麻醉下施行剖宫产术。术毕随机分为镇痛组和对照组各30例：镇痛组行硬膜外镇痛,注入0．075％罗哌卡因和0．009％吗啡复合液（2ml／h）持续48h镇痛;对照组术毕拔出硬膜外导管。采用放射免疫法测定血浆泌乳素（PRL）,视觉模拟评分（VAS）估计镇痛效果。结果镇痛组VAS明显低于对照组（P〈0．01）,镇痛组术后PRL较术前升高（P〈0.05）,术后24～48h镇痛组PRL高于对照组（P〈0．05或P〈0．01）;镇痛组初乳时间较对照组提前（P〈0．01）,镇痛组肠蠕动恢复时间明显快于对照组（P〈0．01）,术后生命征平稳,无恶心、呕吐、头痛、肢体麻木发生。结论剖宫产术后低浓度罗哌卡因复合吗啡持续硬膜外镇痛效果确切安全,能促进PRL分泌,初乳时间提前,加快肠蠕动恢复。     

Role of Prolactin in Pregnancy Hypertension

In 51 patients with pregnancy hypertension (H) and 51 normotensive gravid women (N), matched for age of gestation, plasma prolactin was measured at 8.30 am (PRL1) and 9.30 am (PRL2) in basal conditions and after 10 minutes of upright posture (PRL3). While in N there was a fall from PRL1 to PRL2 which was nonsignificant, in H there was a significant fall from PRL1 to PRL2. With upright posture there was a further decrease in prolactin in N and a significant increase in H. With multiple regression analysis, systolic and diastolic blood pressure did not show any independent relations with PRLl, PRL2 and PRL3, while serum proteins and proteinuria showed a significant relation with PFU1, as did serum proteins, serum potassium and serum urate with PRL2 and serum urate with PRL3. As has been suggested in primary hypertension, a certain increase in peripheral sympathetic tone, dependent on a decreased central dopaminergic activity, may be present in patients who develop pregnancy hypertension compared to normotensive pregnant controls and may be involved in the pathogenesis of pregnancy hypertension.

Preliminary results have been presented at the “16th Congress of the Society for the Study of Pathophysiology of Pregnancy-Organisation Gestosis”-Aachen, Germany, June 1984.