ADRENALINE INFUSION AND ADRENOCORTICOTROPHIN (ACTH) AND CORTISOL RELEASE IN NORMOTENSIVE AND HYPERTENSIVE MAN

1. Adrenaline causes ACTH release from cultured rat pituitary corticotrophs (Vale et al. 1983) and there is evidence that it causes ACTH release in rats in vivo (Plotsky et al. 1985). 2. The present study examined the effects of intravenous adrenaline infusion with and without simultaneous administration of the known ACTH secretagogue, arginine vasopressin, in normotensive and mild essential hypertensive men on their plasma ACTH and cortisol levels. 3. Low dose adrenaline infusion (0.013 microgram/kg per min) does not cause ACTH or cortisol release, but appears to blunt the ACTH and cortisol rise caused by arginine vasopressin (0.14 pressor units/kg, i.m.).     

L-TYPE CALCIUM CHANNELS AND CRH-MEDIATED ACTH AND CORTISOL RELEASE IN HUMANS

1. The effect of pretreatment with nifedipine on naloxone-stimulated corticotrophin-releasing hormone (CRH)-induced adrenocorticotrophin (ACTH) release in humans was investigated. The mean peak plasma ACTH and cortisol levels and the mean peak change in cortisol levels from basal were significantly lower in the nifedipine/naloxone test than in the naloxone alone test. The integrated areas under the ACTH-time and cortisol-time curves were reduced by 33 and 49%, respectively, in the nifedipine/naloxone test compared with the naloxone alone test. These results correlate well with published in vitro studies. 2. Acute administration of oral nifedipine partially inhibited naloxone-stimulated ACTH and cortisol release, probably by blockade of plasma membrane voltage-dependent L-type calcium channels normally activated following binding of CRH to pituitary corticotroph receptors. 3. Naloxone-induced CRH release may replace insulin hypoglycaemia testing of pituitary ACTH reserve in humans.     

POTENTIATION OF FENFLURAMINE-INDUCED ACTH RELEASE IN MAN BY NALOXONE

1. This study set out to compare the effect of the combination of fenfluramine (Fen) and naloxone (Nal) on ACTH and cortisol release with each of these agents alone in six normal volunteers. Three protocols were used: 1.5 mg/kg bodyweight oral Fen; 125 micrograms/kg bodyweight i.v. Nal; oral Fen plus i.v. Nal 135 min later. Plasma ACTH and cortisol were measured at intervals of 285 min over each test. 2. The mean peak levels and mean peak changes from basal in plasma ACTH and cortisol were significantly greater in the combination test (Fen/Nal) than in either the Fen alone or the Nal alone tests. Fen and Nal given together cause a synergistic release of ACTH and cortisol as determined by the areas under the ACTH-time and cortisol-time curves for Fen/Nal compared to the sums of Fen alone plus Nal alone curves for ACTH and cortisol. 3. We conclude that Fen and Nal acting synergistically work through different and potentiating mechanisms at the hypothalamic, central nervous system and/or pituitary levels to cause ACTH release.     

INHIBITION OF SEROTONIN-INDUCED ACTH RELEASE IN MAN BY CLONIDINE

1. Clonidine, an alpha 2-adrenergic agonist, is thought to inhibit noradrenergic neuronal activity (NNA) in the central nervous system (CNS) by a presynaptic alpha 2-receptor mechanism. Central NNA is thought to be the primary monoaminergic stimulus to pituitary ACTH release. Fenfluramine, a serotonin releasing agent and uptake inhibitor, causes ACTH release in normal man. 2. The present study investigated the effect of clonidine on fenfluramine-induced ACTH release in six normal volunteers. Four protocols were used: 1.5 mg/kg body weight oral fenfluramine; 4.3 micrograms/kg body weight oral clonidine; oral clonidine + oral fenfluramine 1 h later; placebo clonidine. Plasma ACTH and cortisol were measured at intervals for 5 h after clonidine and for 4 h after fenfluramine. 3. The mean plasma ACTH and cortisol levels and the mean maximal changes in these levels were significantly lower during the clonidine + fenfluramine test than during fenfluramine alone. Plasma ACTH and cortisol levels were not lowered significantly more by clonidine than by placebo. 4. In conclusion, clonidine blocked the ACTH-releasing activity of fenfluramine in normal humans. This inhibition of active ACTH release may result from clonidine blockade of fenfluramine-induced activation of central NNA. Clonidine alone was no more effective than placebo in lowering plasma ACTH and cortisol.     

NALOXONE-INDUCED ACTH RELEASE IN MAN IS INHIBITED BY CLONIDINE

1. Adrenergic mechanisms play an important role in regulation of ACTH release. We used the alpha 2-adrenergic agonist, clonidine, as a central nervous system inhibitor of ACTH release to see if it would alter naloxone-induced ACTH secretion in normal human volunteers. 2. There was a significant blunting of the mean peak level of ACTH and the mean peak change of ACTH from basal as well as the area under the ACTH-time curve when clonidine was given prior to naloxone. 3. We conclude that clonidine, by blocking central noradrenergic pathways, which stimulate corticotropin-releasing hormone secretion, inhibits naloxone-induced ACTH secretion. This suggests that naloxone causes ACTH release through these same central noradrenergic pathways.     

SHORT COMMUNICATION: EFFECTS OF NIFEDIPINE AND BAY-K-8644 ON THE RELEASE OF CATECHOLAMINES FROM THE DOG ADRENAL GLAND IN RESPONSE TO SPLANCHNIC NERVE STIMULATION

1. The effects of nifedipine and Bay-K-8644 on the release of adrenal catecholamines were examined in anaesthetized dogs. 2. Splanchnic nerve stimulation (SNS) at 1 and 3 Hz produced frequency-dependent increases in adrenaline (ADR) and noradrenaline (NA) output determined from adrenal venous blood. 3. Neither nifedipine (10 and 30 μg/kg, i.v.) nor Bay-K-8644 (10 and 30 μg/kg, i.v.) modified the SNS-induced increases in catecholamine output. Basal catecholamine output tended to be increased and decreased by nifedipine and Bay-K-8644, respectively. 4. Nifedipine produced significant decreases in arterial pressure and renal blood flow rate. Bay-K-8644 produced a significant increase in arterial pressure associated with a decrease in renal blood flow rate. 5. These results suggest that dihydropyridine-sensitive calcium channels do not play a major role in adrenal catecholamine release evoked by SNS.     

POTENTIATION OF ACTH HYPERTENSION IN MAN WITH SALT LOADING

ACTH 1 mg/day for 5 days raises systolic blood pressure (SBP) in normotensive and hypertensive subjects on a fixed electrolyte intake of 100 mmol/day sodium (Na) and potassium (K) (Whitworth et al. 1983). The present study examined the effect of Na intake in the high normal range on the haemodynamic and metabolic responses to ACTH. ACTH administration on a 200-300 mmol Na intake increased SBP by 35 mmHg (s.e.m. = 11, n = 5) compared with the 22 mmHg (s.e.m. = 4, n = 12) rise seen on a 100 mmol Na intake in our previous study. These studies suggest that the effects of adrenocortical steroids on blood pressure in man may be magnified by increasing dietary Na intake.     

EFFECT OF FLUMAZENIL ON BASAL AND NALOXONE-STIMULATED ACTH AND CORTISOL RELEASE IN HUMANS

1. Endogenous benzodiazepine receptor ligands are thought to influence the human hypo-thalamic-pituitary-adrenal (HPA) axis and naloxone, a known stimulator of adrenocorticotropic hormone (ACTH) release, is thought to act via release of hypothalamic corticotropin-releasing hormone. 2. The aim of the present study was to assess the influence of endogenous benzodiazepine-receptor ligands by administering flumazenil (Ro 15–1788), a benzodiazepine antagonist, and measuring ACTH and cortisol release, both basal and during naloxone-stimulation. 3. Nine normal volunteers in a placebo-controlled double-blind design were studied. Flumazenil (0.5 mg, i.v. bolus) was given 2 min before naloxone (125 μg/kg bodyweight, i.v. bolus) immunoreactive-adrenocorticotropic hormone (IR-ACTH) and cortisol levels were measured at frequent intervals from 60 min before to 120 min after naloxone injection. 4. Flumazenil had no effect on ACTH and cortisol release when given alone; flumazenil area under the ACTH/time curve (pmol/L.min) = -36.5 ± 63.5 compared with placebo = - 53.5± 31.8, flumazenil area under the cortisol/time curve (nmol/L.min x 10^?3) = - 2.4 ± 2.4 compared with placebo - 0.56 ± 1.4. Flumazenil did not change the ACTH and cortisol release achieved with naloxone; naloxone area under the ACTH/time curve (pmol/L. min) = 327.8 ± 61.7 compared with flumazenil/naloxone = 366.3 ± 88.1, naloxone area under the cortisol/time curve (nmol/L.minX 10^?3) = 12.2 ± 3.4 compared with naloxone/flumazenil = 10.5±2.1. 5. The authors conclude that flumazenil does not modify basal or stimulated ACTH and cortisol release in healthy humans. This would suggest that endogenous benzodiazepine-like ligands and the benzodiazepine/gamma-aminobutyric acid receptor complex do not tonically influence the hypothalamic-pituitary-adrenal axis.     

胃漂浮缓释片研究Ⅰ硝苯啶胃漂浮缓释片的制备与性质

以 PVP、PVA 为辅料制备了一种能漂浮在胃液上的硝苯啶片剂,用自制的石英弹簧秤比较了辅料配比不同时片剂的漂浮性能,片中硝苯啶以接近零级模式在8h 内释药90%。     

EFFECTS OF ARGININE VASOPRESSIN, ANGIOTENSIN II AND ENDOTHELIN-1 ON THE RELEASE OF BRAIN NATRIURETIC PEPTIDE IN VIVO AND IN VITRO

1. The stimulatory effects of the vasoactive peptides arginine vasopressin (AVP), angiotensin II (AII) and endothelin-1 (ET-1) on the release of brain natriuretic peptide (BNP) were investigated in anaesthetized rats and in cultured rat atrial and ventricular cardiocytes. 2. A bolus injection of AVP induced a dose-dependent increase in plasma immunoreactive (ir)-BNP concentration in rats. AII induced a rapid and transient elevation in the ir-BNP level, while the increase produced by ET-1 was long-lasting. The elevation of the plasma ir-BNP concentration after stimulation by these three vasoconstrictors appeared to be paralleled by the elevation in mean blood pressure. 3. In the in vitro study, the rat atrial and ventricular cardiocytes both secreted ir-BNP into the medium in a time-dependent manner. ET-1 clearly stimulated the secretion of ir-BNP in both atrial and ventricular cardiocytes. In contrast, AVP and AII had no stimulatory effect in vitro. 4. Reverse-phase high performance liquid chromatography of the rat plasma and culture medium revealed a single major ir-BNP component that corresponded to synthetic rat BNP-45. 5. These observations indicate that AVP, AII and ET-1 stimulate the release of ir-BNP (probably rat BNP-45) through a change in blood pressure. In addition, ET-1 may also induce ir-BNP release through direct stimulation. As a cardiac hormone secreted from ventricles as well as atria, rat BNP may play a role in the regulation of blood pressure against the pressor effects of AVP, AII and ET–1.     

CORTISOL PRODUCTION BY ALDOSTERONE-PRODUCING ADENOMAS IN VITRO

1. In vitro short-term production of cortisol by dispersed tumour and non-tumorous adrenal cortical cells was measured with and without added angiotensin II (AII) or adrenocorticotrophin (ACTH) in adrenals removed from five patients with primary aldosteronism. 2. Aldosterone-producing adenomas (APA) were classified as angiotensin responsive (AII-R) or angiotensin unresponsive (AII-U) based on pre-operative behaviour in vivo. 3. Cortisol was produced by both tumour and cortex in vitro without stimulation, and significantly more cortisol was generated by the cortex. 4. Addition of AII significantly increased cortisol production by both tumour and cortex to an equal extent. 5. Addition of ACTH also significantly increased cortisol production by both tumour and cortex, but tumours were more responsive than cortex. The response to ACTH exceeded the response to angiotensin in both tumour and cortex. 6. There was no obvious difference between AII-R and AII-U APA in terms of cortisol production.     

硝苯吡啶缓释片的人体药物动力学及生物利用度

用ＨＰＬＣ法测定血中硝苯吡淀浓度，对进口的硝苯吡啶务产的硝苯吡啶缓释片进行健康人药物动力学和生物利用度研究，所得数据经３Ｐ８７软件处理。结果显示：硝苯吡啶以二室模型进行分布和消除，进口硝苯吡啶的生物利用度明显优于国产硝苯吡啶，消除半衰期长于国产硝苯吡啶。     

长期吸烟者血浆皮质醇及β-内啡肽的变化

目的·· :探讨长期吸烟者在戒烟前后血浆皮质醇和 β-内啡肽水平的变化及形成机制。方法·· :于戒烟前后采集长期吸烟者静脉血 ,用放射免疫方法检测血浆皮质醇及血浆 β-内啡肽的含量。结果·· :长期吸烟者的血浆皮质醇(227.82ng·ml-1±s40.03ng·ml-1)及血浆 β-内啡肽(14.68ng·ml-1±s4.48ng·ml-1)明显高于正常组 ;戒断后长期吸烟组的血浆皮质醇(271.92ng·ml-1±s32.19ng·ml-1)明显升高 ,而血浆 β-内啡肽(8.16ng·ml-1±s4.97ng·ml-1)明显降低。结论·· :血浆皮质醇及 β-内啡肽可作为判断戒烟治疗效果的指标之一 ,而改善内源性阿片肽系统及下丘脑 -垂体 -肾上腺轴的功能可能对戒烟有助。     

INTERACTION BETWEEN EPIDERMAL GROWTH FACTOR AND ARGININE VASOPRESSIN IN RENAL MEDULLARY MEMBRANES

1. Epidermal growth factor is a potent mitogen that causes natriuresis, diuresis and inhibition of arginine vasopressin-induced water reabsorption. 2. The aim of this study was to determine any interaction between epidermal growth factor and the V1 (vascular) and/or V2 (antidiuretic) arginine vasopressin receptor subtypes. 3. Radioligand binding displacement assays demonstrated that although arginine vasopressin related peptides displaced both radioligands from renal medullary membranes at low concentrations epidermal growth factor displaced neither. 4. Arginine vasopressin V2 receptor second messenger cyclic adenosine monophosphate (CAMP) production was inhibited by epidermal growth factor (IC₅₀ 2 ± 10^?7 mol/L) as was sodium fluoride cAMP production but only at much higher concentrations. 5. Therefore the diuretic effect of epidermal growth factor is not via direct antagonism of arginine vasopressin receptors but seems mediated via inhibition of the V2 second messenger system.     

ACTH HYPERTENSION IN THE RAT: ROLE OF KIDNEY AND GONADS

1. Adrenocorticotrophin (ACTH) administration produces an adrenally dependent rise in blood pressure in rats. 2. The haemodynamic and metabolic effects of ACTH were examined in nephrectomized, 5/6 nephrectomized and orchidectomized male Sprague-Dawley rats and sham operated controls. 3. Reduction in renal mass did not increase the blood pressure rise produced by ACTH. 4. Gonadectomy did not reduce the blood pressure rise produced by ACTH, which was slightly higher in castrated animals.     

DOSE-RESPONSE RELATIONSHIPS FOR ADRENOCORTICOTROPHIN-INDUCED HYPERTENSION IN MAN

Adrenocorticotrophin (ACTH), given as long-acting Synacthen depot (Ciba-Geigy), at 1000 micrograms/day, in divided doses 12 hourly, is known to increase blood pressure in man. Fifty micrograms/day of short-acting Synacthen given intravenously produced a rise in blood pressure and may be a threshold dose. Twelve hourly intramuscular injections of short-acting Synacthen over the dose range 100-400 micrograms/day was not sufficient to raise blood pressure.     

INTERRELATIONSHIP BETWEEN CORTISOL AND ATRIAL NATRIURETIC FACTOR IN THE IMMATURE OVINE FETUS

1. In chronically cannulated ovine fetuses (100-130 days of gestation) the infusion of cortisol (86.7 +/- 15 micrograms/h for 4 h) or human atrial natriuretic factor (ANF; 4.4 micrograms for 2 h) resulted in highly significant increases in the excretion of sodium, chloride, potassium and water. 2. Cortisol had no significant effect on fetal plasma ANF concentrations. All values are mean and s.e.m. Plasma immunoreactive ANF was 53 +/- 5 and 67.3 +/- 13 pmol/L in the 4 h saline infused fetuses, and 51.3 +/- 14.3 and 74 +/- 13.3 pmol/L in cortisol-infused fetuses (n = 7). A separate group of fetuses received 2 h infusions of saline or hANF (4.4 micrograms/h), and plasma IR-ANF values were measured (n = 3). The values, at 0, 60, 90 and 120 min were, respectively, 19.7 +/- 3, 17.3 +/- 0.7, 18.7 +/- 3.7 and 20.7 +/- 3.7 pmol/L in the saline infused group, and 25.3 +/- 5.3, 80.7 +/- 32.3, 123.3 +/- 4.3 and 100 +/- 15 pmol/L in the ANF-infused fetuses. 3. Blood cortisol concentrations, in fetuses infused for 4 h with 0.9% NaCl, were 3.1 +/- 0.8 nmol/L (n = 7); in fetuses infused with 0.9% NaCl for 2 h were 3.6 +/- 1 nmol/L (n = 3); in fetuses infused for 4 h with cortisol were 19.9 +/- 1.9 nmol/L (n = 7); and in fetuses infused with hANF for 2 h were 6.0 +/- 3.0 nmol/L (n = 5). 4. There was no effect of fetal hANF infusion on maternal or fetal blood aldosterone concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)