Atrial Natriuretic Peptide Secretion from Fetal Rat Diencephalon in Culture

The presence of a distinct brain pool of the atrial natriuretic peptides (ANP) has been established. To determine the molecular forms and regulation of secretion of ANP, we studied fetal rat diencephalic neurons and glia in primary culture. ANP immunoreactivity determined by radioimmunoassay was found only in the neuron predominant cultures. The neurons contained mainly ANP (103–126) and less ANP (102–126), but secreted only ANP (103–126) into the medium after potassium and glutamate-dependent depolarization. Little, if any, ANP (99–126), the predominant form which circulates in plasma and originates from the heart, was secreted. The ability of potassium and glutamate to cause a mean 50% increase of ANP secretion above baseline was abolished after deleting calcium chloride from the medium. In contrast, hypo- or hyperosmolarity or increased sodium content in the incubation medium did not influence ANP secretion. These studies indicate that regulative secretion of ANP occurs from primary cultures of predominantly diencephalic neurons, probably accounting for the high concentrations of these peptides in this area of the brain. The forms of ANP contained within the cells and secreted after depolarization are different from ANP secreted from neonatal rat atrial myocytes. In contrast to myocytes, varying sodium or osmolarity did not cause ANP secretion. We postulate that influences on ANP production/secretion in the brain may be distinct from the heart.     

Recurrent Seizures Alter Renal Function and Plasma Atrial Natriuretic Peptide Levels in Rats

Summary: Status epilepticus can lead to impaired renal function, which has been attributed to complications of myoglobinuria. We confirmed changes in renal function in the absence of myoglobinuria by measuring renal hemodynamics, fluid and electrolyte excretions, and plasma levels of renin and atrial natriuretic peptide (ANP) before and after a 30-min period of recurrent generalized seizures in anesthetized, paralyzed rats. Renal plasma flow (RPF), renal blood flow (RBF) and glomerular filtration rate (GFR) decreased by ∼60% after seizures. In contrast, urinary sodium excretion, urine flow, and plasma ANP levels increased approximately threefold. Urinary potassium excretion and plasma renin levels were unchanged. Renal function is profoundly altered after 30 min of seizures, primarily due to intense renal vasoconstriction precipitating a dramatic reduction in GFR. The concomitant increases in sodium and urine excretion may be mediated by the marked increase in plasma ANP levels. The decreases in GFR and RBF might contribute to the renal failure observed in some patients after status epilepticus.     

An Enkephalinergic Mechanism for the Hypothalamic Effect of Atrial Natriuretic Peptide to Inhibit Luteinizing Hormone Secretion

Previous studies have demonstrated a hypothalamic site of action of atrial natriuretic peptide (ANP) to inhibit luteinizing hormone and an opioid mechanism has been suggested. We have identified the paraventricular nucleus as at least one locus of action of ANP since site-specific injection of 0.1 nmol, bilaterally into this nucleus, but not the medial preoptic nuclei or arcuate nucleus, resulted in a significant inhibition of plasma levels in conscious, ovariectomized rats 90 and 120 min later. This paraventricular site of action suggested an involvement of endogenous enkephalins. The stable enkephalin analog, [D-Pen^2.5]enkephalin, when injected into the third ventricle in a dose of 1.0 nmol, produced a significant and transient inhibition of luteinizing hormone secretion similar to that seen following injection of 2.0 nmol ANP. Pretreatment of the rats 15 min before peptide injection with the selective 5 opioid antagonist naltrindole (50 μg/2 μl saline) completely prevented the luteinizing hormone-inhibiting effects of both ANP and the enkephalin analog, δ opioid blockade failed to prevent the prolactin-inhibiting effect of ANP but did reverse the prolactin-stimulating effect of [D-Pen^2.5]enkephalin. Our results suggest a paraventricular nucleus site of action of ANP in addition to probable effects in the median eminence and indicate the possible enkephalinergic mediation of the peptide's ability to inhibit luteinizing hormone secretion.     

Effect of Atrial Natriuretic Peptide on the Vasopressin Response to Osmotic and Hemorrhagic Stimuli in Dogs

Effect of atrial natriuretic peptide (ANP) on the vasopressin response to osmotic stimulation (Experiment I) as well as to hemorrhage (Experiment II) was investigated in anesthetized dogs. Moreover, cardiovascular function and renal water and electrolyte excretion were studied. In Experiment I, 2.5 M NaCI, containing 0.02 μg.kg ¹ of ANP, was infused intravenously at a rate of 0.2 ml.kg^?1, min ¹ after one bolus injection of 0.75 μg.kg ¹ ANP (HSA group). In the control group, 2.5 M NaCI alone (HS group) was infused. The infusion was continued for 75 min. In Experiment II, 0.15 M NaCI, containing the identical dose of ANP to Experiment I (HA group), or 0.15 M NaCI alone (H group) was infused intravenously during bleeding at a rate of 1 ml.kg^?1.min ^?1 for 40 min. In Experiment I, infused ANP suppressed the vasopressin response to a mild osmotic stimulation, but not to a strong osmotic stimulation and attenuated ANP release and a rise in arterial and central venous pressures in response to plasma volume expansion, without the enhanced natriuresis. In Experiment II, infused ANP neither impaired the vasopressin response to bleeding nor potentiated a fall in mean arterial pressure and central venous pressure. In conclusion, ANP at physiological and/or supraphysiological range may suppress the vasopressin response to a mild osmotic stimulation, but not to a strong osmotic stimulation and to hemorrhage. In addition, ANP given intravenously may attenuate ANP release and a rise in blood pressure without any natriuresis.     

Atrial Natriuretic Peptide, Cyclic GMP Analogues and Modulation of Guanylyl Cyclase do not Alter Stimulated POMC Peptide Release From Perifused Rat or Sheep Corticotrophs

Corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP) are two potent stimulators for secretion of proopiomelanocortin (POMC)-derived hormones, from corticotrophs. CRH also stimulates POMC synthesis. Atrial natriuretic peptide (ANP) has been reported to inhibit POMC peptide release and is thought to act through cGMP signalling pathways. A multicolumn cell perifusion system was used to investigate the role of cGMP signalling pathways in CRH- and AVP-stimulated POMC peptide release from primary cultures of ovine or rat anterior pituitary cells. The CRH and/or AVP stimulations were applied at 30 min intervals as 5 min pulses, and the various treatments were infused over a period of 50 min, overlapping with 2 of the stimulations. ANP (10 nM) had no effect on β-endorphin (βEP) release from ovine cells, stimulated by 0.5 nM CRH and 5 nM AVP together, or 5 nM CRH and 50 nM AVP separately. Rat anterior pituitary cells were stimulated with 0.05 nM CRH/0.5 nM AVP or 0.5 nM CRH/5 nM AVP and treated with 1 nM or 10 nM ANP, respectively. No inhibition of ACTH or βEP was observed. Similarly, the nitric oxide donors molsidomine (100 μM), SIN-1 (100 μM) and NaNO₂ (100 μM) did not inhibit βEP release stimulated by 0.5 nM CRH/5 nM AVP in ovine cells. The cGMP analogues 8-bromo-cGMP (10 μM and 100 μM) and dibutyryl cGMP (100 μM) also had no effect on βEP and ACTH release from ovine or rat anterior pituitary cells. Dexamethasone (8 μM), a synthetic glucocorticoid known to block POMC synthesis and secretion of βEP and ACTH by a distinct mechanism, was used as a control and suppressed CRH/AVP-stimulated βEP secretion from ovine anterior pituitary cells. These results contrast with some previous studies and demonstrate that the cGMP signalling pathway in sheep or rat anterior pituitary cells does not directly inhibit secretion of POMC-derived hormones from corticotrophs.     

Psychosocial Correlates of Insomnia in An Adolescent Population

This study examines the nature of the relationship between psychosocial factors and insomnia complaints in an adolescent non-clinical population. It is a cross-sectional study of a stratified sample of 2,195 Greek adolescent high-school students. Subjects were given the Athens insomnia scale, the Symptom Checklist scale (SCL-90-R) and a questionnaire concerning demographic characteristics. None of the subjects had received help for insomnia complaints or other overt psychopathology. Adolescents classified as suffering from insomnia presented higher levels of general psychopathology. Age, tobacco and alcohol use, self-reported patterns of communication in the family, perceived economic status and school performance were identified as correlates of the insomnia complaints. A significant number of adolescents fail to receive appropriate treatment for insomnia. Psychosocial correlates are important factors to consider when faced with insomnia complaints in this age group. More research is needed in important timelines in the developmental history of a young adult.     

Atrial Natriuretic Factor is Released into Hypophysial Portal Blood: Direct Evidence that Atrial Natriuretic Factor may be a Neurohormone Involved in Hypothalamic Pituitary Control

Atrial natriuretic factor (ANF) is produced in atriomyocytes (1, 2), released as a 28 amino-acid peptide into the systemic circulation and probably plays an important role in fluid and electrolyte balance (3, 4). The facts that immunoreactive ANF (ir-ANF) is also present in nerve terminals in the external layer of the median eminence (ME) (5), ir-ANF can be released from the hypothalamus in vitro by potassium depolarization (6) and specific ANF binding sites are present at a high concentration in rat pituitary tissue (7) suggest that ANF may be involved in hypothalamic-pituitary regulation. We report here that ir-ANF concentrations in hypophysial portal blood are about two to four times greater than in peripheral plasma from hypophysectomized as well as pituitary-intact adult female rats. These results show for the first time that ir-ANF is secreted from the hypothalamus into the hypophysial portal circulation at a concentration (≈10⁻⁹ M) consistent with a role for ANF as a hypothalamic-pituitary regulator or modulator.     

Psychosocial Correlates of Suicidal Ideation in Rural South African Adolescents

Suicide is a prevalent problem among young people in Southern Africa, but prevention programs are largely absent. This survey aimed to identify the behavioral and psychosocial correlates of suicidal ideation among adolescents in Limpopo. A two-stage cluster sample design was used to establish a representative sample of 591 adolescents. Bivariate correlations and multiple linear regression analyses were conducted. Findings show that suicidal ideation is prevalent among adolescents. The psychosocial factors perceived social support and negative feelings about the family and the behavioral factors forced sexual intercourse and physical violence by the partner were found to increase the risk of suicidal ideation. Depression mediated the relationship between these psychosocial and behavioral risk factors and suicidal ideation. This study increased our understanding of the psychosocial and behavioral predictors of adolescent suicidal ideation. The findings provide target points for future intervention programs and call for supportive structures to assist adolescents with suicidal ideation.     

Major Depressive Disorder during Teenage Pregnancy: Socio-demographic,Obstetric and Psychosocial Correlates

ObjectivesTo describe the prevalence of Major Depressive Disorder (MDD) during pregnancy in teenage mothers and to assess its association with socio-demographic characteristics, obstetric history and psychosocial variables.MethodsA cross-sectional study was conducted with a sample of pregnant teenagers enrolled in the national public health system in the urban area of Pelotas, southern Brazil. MDD was assessed with the Mini International Neuropsychiatric Interview, the Abuse Assessment Screen was used to identify physical abuse within the last 12 months and during pregnancy, and social support was assessed with the Medical Outcomes Survey Social Support Scale.ResultsForty-three (4.94%) potential subjects refused to participate, resulting in 828 total participants. The prevalence of MDD was 17.8%, 9.2% reported they had been subjected to violence within the last 12 months, while 5.8% had suffered violence during pregnancy, and the mean (SD) overall social support score was 87.40 (11.75). After adjustment, we found the highest incidence of MDD in adolescents with less than 8 years of education, followed by those with previous episodes of MDD and those with lower overall social support.ConclusionsMDD is a relatively common condition in pregnant teenagers and appears to be more prevalent in young mothers who are both socioeconomically and psychosocially underprivileged.     

Brain Natriuretic Peptide Concentrations After Aneurysmal Subarachnoid Hemorrhage: Relationship with Hypovolemia and Hyponatremia

Background  

Hyponatremia and hypovolemia occur often after aneurysmal subarachnoid hemorrhage (SAH) and are associated with poor outcome. The authors investigated whether brain natriuretic peptide (BNP) is related to hypovolemia and hyponatremia after SAH and whether it can differentiate between hypovolemic and non-hypovolemic hyponatremia.     

急性脑卒中与血清N末端B型利钠肽相关性的研究

目的 探讨急性脑卒中患者的血清N末端B型利钠肽 (NT-pro BNP)的变化,评价血清NT-pro BNP测定的临床意义.方法 74例患者分别为急性脑梗死 (CI) (42例)和急性脑出血 (ICH)组 (32例),根据入院时NIHSS评分分为轻度、中度和重度3个亚组,采用ECLIA法检测发病48 h内 (急性期)及发病第21天 (亚急性期)的血清NT-pro BNP水平,与健康对照组进行比较,比较急性期与亚急性期间、各亚组间的血清NT-pro BNP水平差异.结果 CI组和ICH组急性期血清NT-pro BNP显著高于对照组 (P<0.01),并在亚急性期显著下降(P<0.01);各亚组间急性期血清NT-pro BNP水平均有显著统计学差异 (P<0.01).结论 急性期脑卒中患者急性期血清NT-pro BNP水平与病情程度相关.     

Release of Atrial Natriuretic Factor from Intact and Hypophysectomized Rat Hypothalamic Expiants

Experiments examined release of atrial natriuretic factor (ANF), measured by radioimmunoassay, from acutely prepared explants of rat hypothalamus maintained in vitro by intra-arterial perfusion of artificial cerebrospinal fluid. Perfusates collected from intact preparations contained 6.1 ± 0.6 pg (mean ± SEM) of ANF per 2-min sample. Following a 3-min infusion of noradrenaline (60 μM), ANF release increased significantly (P<0.05) to 11.4±1.4 pg/sample. Media collected from hypophysectomized preparations showed the same basal ANF release (6.8 ± 0.9 pg/sample) as intact preparations, but demonstrated no significant increase after noradrenaline infusions. Levels of spontaneous ANF release were not appreciably affected by the absence of the paraventricular nuclei and/or the anteroventral third ventricle area.
Extracted material from the perfusate by reverse-phase high performance liquid chromatography revealed two main peaks of immunoreactive ANF: a small molecular weight form that coeluted with synthetic ANF (99–126) and with similar biological activity in a radioreceptor assay, and a larger molecular weight form with the same elution profile as the ANF (1–126) prohormone.
These observations indicate that the ANF released from perfused rat hypothalamic explants contains distinct contributions from the hypothalamus (sites undetermined) and the neurointermediate lobe.