The neuropeptide substance P regulates aldosterone secretion in human adrenals.

Aldosterone, produced by the adrenals and under the control of plasma angiotensin and potassium levels, regulates hydromineral homeostasis and blood pressure. Here we report that the neuropeptide substance P (SP) released by intraadrenal nerve fibres, stimulates aldosterone secretion via binding to neurokinin type 1 receptors (NK1R) expressed by aldosterone-producing adrenocortical cells. The action of SP is mediated by the extracellular signal-regulated kinase pathway and involves upregulation of steroidogenic enzymes. We also conducted a prospective proof-of-concept, double blind, placebo-controlled clinical trial aimed to investigate the impact of the NK1R antagonist aprepitant on aldosterone secretion in healthy male volunteers (EudraCT: 2008-003367-40, ClinicalTrial.gov: NCT00977223). Participants received during two 7-day treatment periods aprepitant (125 mg on the 1st day and 80 mg during the following days) or placebo in a random order at a 2-week interval. The primary endpoint was plasma aldosterone levels during posture test. Secondary endpoints included basal aldosterone alterations, plasma aldosterone variation during metoclopramide and hypoglycaemia tests, and basal and stimulated alterations of renin, cortisol and ACTH during the three different stimulatory tests. The safety of the treatment was assessed on the basis of serum transaminase measurements on days 4 and 7. All pre-specified endpoints were achieved. Aprepitant decreases aldosterone production by around 30% but does not influence the aldosterone response to upright posture. These results indicate that the autonomic nervous system exerts a direct stimulatory tone on mineralocorticoid synthesis through SP, and thus plays a role in the maintenance of hydromineral homeostasis. This regulatory mechanism may be involved in aldosterone excess syndromes.

Intratumoral heterogeneity of steroidogenesis in aldosterone-producing adenoma revealed by intensive double- and triple-immunostaining for CYP11B2/B1 and CYP17.

INTRODUCTION: Cytochrome P450 11B2 (CYP11B2) plays a pivotal role in aldosterone synthesis, while cytochrome P450 11B1 (CYP11B1) and cytochrome P450 17A1 (CYP17) are involved in cortisol synthesis in normal human adrenal glands. However, their detailed distribution in aldosterone-producing adenoma (APA) remains incompletely settled. MATERIALS AND METHODS: We examined the status of CYP11B1/CYP11B2 and CYP11B2/CYP17A1 expressions in 27 APA (double staining) cases and 21 APA (triple staining) cases by using immunofluorescence staining and semi-quantitative evaluation. RESULTS: Tumor cells co-expressing CYP11B1/B2 (hybrid cell type A), CYP11B2/17 (hybrid cell type B), CYP11B1/17 (hybrid cell type C), and CYP11B1/B2/17 (triple-positive cell) were identified. The area and cell number of these cells were relatively small, but the size of individual hybrid cells were different between three hybrid cell types (A/B/C) and triple-positive cells. CONCLUSION: The presence of hybrid cells indicated the marked intratumoral heterogeneity of steroidogenesis in APAs, particularly in those producing glucocorticoids and mineralocorticoids.

Adrenal steroidogenesis and congenital adrenal hyperplasia.

Adrenal steroidogenesis is a dynamic process, reliant on de novo synthesis from cholesterol, under the stimulation of ACTH and other regulators. The syntheses of mineralocorticoids (primarily aldosterone), glucocorticoids (primarily cortisol), and adrenal androgens (primarily dehydroepiandrosterone and its sulfate) occur in separate adrenal cortical zones, each expressing specific enzymes. Congenital adrenal hyperplasia (CAH) encompasses a group of autosomal-recessive enzymatic defects in cortisol biosynthesis. 21-Hydroxylase (21OHD) deficiency accounts for more than 90% of CAH cases and, when milder or nonclassic forms are included, 21OHD is one of the most common genetic diseases.

Extra-adrenal glucocorticoids and mineralocorticoids: evidence for local synthesis, regulation, and function.

Glucocorticoids and mineralocorticoids are steroid hormones classically thought to be secreted exclusively by the adrenal glands. However, recent evidence has shown that corticosteroids can also be locally synthesized in various other tissues, including primary lymphoid organs, intestine, skin, brain, and possibly heart. Evidence for local synthesis includes detection of steroidogenic enzymes and high local corticosteroid levels, even after adrenalectomy. Local synthesis creates high corticosteroid concentrations in extra-adrenal organs, sometimes much higher than circulating concentrations. Interestingly, local corticosteroid synthesis can be regulated via locally expressed mediators of the hypothalamic-pituitary-adrenal (HPA) axis or renin-angiotensin system (RAS). In some tissues (e.g., skin), these local control pathways might form miniature analogs of the pathways that regulate adrenal corticosteroid production. Locally synthesized glucocorticoids regulate activation of immune cells, while locally synthesized mineralocorticoids regulate blood volume and pressure. The physiological importance of extra-adrenal glucocorticoids and mineralocorticoids has been shown, because inhibition of local synthesis has major effects even in adrenal-intact subjects. In sum, while adrenal secretion of glucocorticoids and mineralocorticoids into the blood coordinates multiple organ systems, local synthesis of corticosteroids results in high spatial specificity of steroid action. Taken together, studies of these five major organ systems challenge the conventional understanding of corticosteroid biosynthesis and function.

The role of adrenal steroidogenesis in arterial hypertension.

Adrenal aldosterone production, the major regulator of salt and water retention, is discussed with respect to hypertensive diseases. Physiological aldosterone production is tightly regulated, either stimulated or inhibited, in the adrenal zona glomerulosa by both circulating factors and/or by locally derived endothelial factors. Arterial hypertension caused by volume overload is the leading clinical symptom indicating increased mineralocorticoid hormones. Excessive aldosterone production is seen in adenomatous disease of the adrenals. The balance between stimulatory/proliferative and antagonistic signaling is disturbed by expression of altered receptor subtypes in the adenomas. Increased aldosterone production without a detectable adenoma is the most frequent form of primary aldosteronism. Both increased sensitivity to agonistic signals and activating polymorphisms within the aldosterone synthase gene (CYP11B2) have been associated with excessive aldosterone production. 17alpha-Hydroxylase deficiency and glucocorticoidremediable aldosteronism can also cause excessive mineralocorticoid synthesis. In contrast, the severe form of pregnancy-induced hypertension, preeclampsia, is characterized by a compromised volume expansion in the presence of inappropriately low aldosterone levels. Initial evidence suggests that compromised CYP11B2 is causative, and that administration of NaCl lowered blood pressure in pregnant patients with low aldosterone availability due to a loss of function.

Hyperreninemic hypoaldosteronism syndrome, plasma concentrations of interleukin-6 and outcome in critically ill patients with liver cirrhosis.

OBJECTIVE: To investigate the relation between the adrenal production of gluco- and mineralocorticoids, the inflammatory status and the outcome in critically ill patients with liver cirrhosis. DESIGN: Prospective descriptive study. SETTING: Medical intensive care unit (ICU) in a university hospital. PATIENTS: Fifty consecutive patients with liver cirrhosis. INTERVENTIONS: A corticotropin stimulation test within 12h following ICU admission. Plasma cortisol concentration was measured before and after the test. Renin and aldosterone concentrations, as well as interleukin-6 (IL-6) level to assess the pro-inflammatory status, were measured only before the test. Impaired adrenal function was defined as cortisol response to the test less than 9microg/dl. Hyperreninemic hypoaldosteronism syndrome was defined as basal renin over aldosterone ratio (RRA) higher than 2. MEASUREMENTS AND RESULTS: Forty-one (82%) patients had impaired adrenal function, and 26 patients (52%) presented with RRA > 2. Patients with RRA > 2 exhibited greater disease severity and organ dysfunction scores at baseline, higher levels of serum renin and IL-6, and a greater ICU mortality rate, but risk-adjusted mortality rates were not different between the two groups. Renin and IL-6 plasma concentrations were positively correlated. Finally, in a Cox regression analysis, independent predictors of 30-day mortality were hyperreninemic hypoaldosteronism syndrome, IL-6 higher than 400pg/ml and severe renal failure. CONCLUSIONS: Adrenal dysfunction was common in critically ill cirrhotic patients. Hyperreninemic hypoaldosteronism syndrome was related to a greater pro-inflammatory status and degree of acute organ failure, and was independently associated with a worse prognosis.

Angiotensin II-induced mitogen-activated protein kinase phosphatase-1 expression in bovine adrenal glomerulosa cells: implications in mineralocorticoid biosynthesis.

Angiotensin II (AngII) stimulates aldosterone biosynthesis in the zona glomerulosa of the adrenal cortex. AngII also triggers the MAPK pathways (ERK1/2 and p38). Because ERK1/2 phosphorylation is a transient process, phosphatases could play a crucial role in the acute steroidogenic response. Here we show that the dual specificity (threonine/tyrosine) MAPK phosphatase-1 (MKP-1) is present in bovine adrenal glomerulosa cells in primary culture and that AngII markedly increases its expression in a time- and concentration-dependent manner (IC(50) = 1 nm), a maximum of 548 +/- 10% of controls being reached with 10 nm AngII after 3 h (n = 3, P < 0.01). This effect is completely abolished by losartan, a blocker of the AT(1) receptor subtype. Moreover, this AngII-induced MKP-1 expression is reduced to 250 +/- 35% of controls (n = 3, P < 0.01) in the presence of U0126, an inhibitor of ERK1/2 phosphorylation, suggesting an involvement of the ERK1/2 MAPK pathway in MKP-1 induction. Indeed, shortly after AngII-induced phosphorylation of ERK1/2 (220% of controls at 30 min), MKP-1 protein expression starts to increase. This increase is associated with a reduction in ERK1/2 phosphorylation, which returns to control values after 3 h of AngII challenge. Enhanced MKP-1 expression is essentially due to a stabilization of MKP-1 mRNA. AngII treatment leads to a 53-fold increase in phosphorylated MKP-1 levels and a doubling of MKP-1 phosphatase activity. Overexpression of MKP-1 results in decreased phosphorylation of ERK1/2 and aldosterone production in response to AngII stimulation. These results strongly suggest that MKP-1 is the specific phosphatase induced by AngII and involved in the negative feedback mechanism ensuring adequate ERK1/2-mediated aldosterone production in response to the hormone.

Possibly simultaneous primary aldosteronism and preclinical Cushing's syndrome in a patient with double adenomas of right adrenal gland.

We reported a rare case of simultaneous primary aldosteronism and preclinical Cushing's syndrome due to unilateral double adrenocortical adenomas in a 57 year-old woman who had had hypertension for the last 10 years. Abdominal computed tomography showed double tumors in her right adrenal gland. Physical findings revealed simple obesity and hypertension, but no other abnormal findings were detected. Laboratory findings demonstrated that serum potassium was 3.8 mmol/l; plasma renin activity, 0.3 ng/ml/h; plasma aldosterone, 100 pg/ml, and aldosterone renin ratio (ARR), 33. Serum cortisol was 15.7 microg/dl. There was no circadian rhythm of serum cortisol, and no suppression of serum cortisol in response to exogenous dexamethasone administration. Right adrenalectomy was performed under laparoscopy. Two well-circumscribed tumors, whose sizes were 21 and 19 mm in greatest diameter, were detected. They were macroscopically composed of a golden-yellow portion admixed with a brown portion, which corresponded to clear cells and compact cells, respectively. Immunohistochemical staining for steroidogenic enzymes demonstrated the presence of all the enzymes involved in corticosteroidogenesis in these two adenomas, indicating that the two adenomas produced both cortisol and mineralocorticoid. Specifically, one adenoma mainly caused excessive production of cortisol as compared to the other one. These findings indicate that overproduction of both cortisol and mineralocorticoid was evident in the two adenomas of the right adrenal gland in immunohistochemical study for steroidogenic enzymes, whereas there was less clinical manifestation of primary aldosteronism and Cushing's syndrome in the present patient.

Monogenic forms of low-renin hypertension.

Hypertension is an important public health problem affecting more than 50 million individuals in the US alone. The most common form, essential hypertension, results from the complex interplay between genetic predisposition and environmental influences. In contrast, monogenic (mendelian) forms of hypertension are caused by single gene mutations that are influenced little, if at all, by environmental factors. Most monogenic forms of hypertension affect either electrolyte transport in the distal nephron, or the synthesis or activity of mineralocorticoid hormones, leading to the common pathogenic mechanisms of increased distal tubular reabsorption of sodium and chloride, volume expansion and hypertension. In young patients with a family history of hypertension who present with severe or refractory hypertension and characteristic hormonal and biochemical abnormalities, the differential diagnosis should include monogenic forms of hypertension. Genetic testing, which is increasingly available, can facilitate timely diagnosis and treatment of these relatively uncommon disorders, such that the underlying defect can be corrected or ameliorated and the long-term consequences of poorly controlled hypertension prevented.

Mineralocorticoid synthesis during the periovulatory interval in macaques.

Ovulation and luteal formation in primates are associated with the sustained synthesis of progesterone. The observed high intrafollicular concentrations of progesterone during the periovulatory interval raise the possibility that this steroid serves as a precursor for mineralocorticoids. The aim of this study was to determine if mineralocorticoids are synthesized by the luteinizing macaque follicle during controlled ovarian stimulation cycles in which follicular fluid and granulosa cell aspirates were obtained before or after an ovulatory hCG bolus. Follicular fluid concentrations of progesterone and 17alpha-hydroxyprogesterone increased within 3 h of an ovulatory hCG bolus. Their respective metabolites, 11-deoxycorticosterone (DOC) and 11-deoxycortisol, were not detectable before an ovulatory stimulus and increased starting at 6 h after hCG, while corticosterone and aldosterone were undetectable. Cortisol was present before and after hCG administration and had increased 2-fold at 24 h after an ovulatory stimulus. The expression of 21-hydroxylase (CYP21A2) mRNA increased within 3 h of hCG administration, while 11beta-hydroxylase-1 (CYP11B1) and 11beta-hydroxylase-2 (CYP11B2) mRNAs were not detectable. 11beta-Hydroxysteroid dehydrogenase-1 (HSD11B1) mRNA had increased at 12 h after hCG administration, and 11beta-hydroxysteroid dehydrogenase-2 (HSD11B2) had decreased by 3 h after hCG administration. Mineralocorticoid receptor mRNA levels did not change following hCG administration, while glucocorticoid receptor mRNA levels increased in response to an ovulatory stimulus. Treatment of granulosa cells with the mineralocorticoid receptor antagonist spironolactone blocked hCG-induced progesterone synthesis in vitro. These data indicate that macaque granulosa cells can synthesize mineralocorticoids in response to an ovulatory stimulus and that the mineralocorticoid receptor plays a key role in steroid synthesis associated with luteinization of macaque granulosa cells.

Effects of anticonvulsants on human p450c17 (17alpha-hydroxylase/17,20 lyase) and 3beta-hydroxysteroid dehydrogenase type 2.

PURPOSE: Women with epilepsy apparently have a higher incidence of polycystic ovary syndrome (PCOS) than do women without epilepsy. Whether the underlying disease or the antiepileptic drug (AED) treatment is responsible for this increased risk is unknown, although clinical reports implicate valproic acid (VPA) as a potential cause. The steroidogenic enzymes 3beta HSDII (3beta-hydroxysteroid dehydrogenase) and P450c17 (17alpha-hydroxylase/17,20 lyase) are essential for C19 steroid biosynthesis, which is enhanced during adrenarche and in PCOS. METHODS: To determine whether the AEDs VPA, carbamazepine (CBZ), topiramate (TPM), or lamotrigine (LYG) directly affect the activities of human 3beta HSDII and P450c17, we added them to yeast expressing human P450c17 or 3beta HSDII and assayed enzymatic activities in the microsomal fraction. RESULTS: Concentrations of VPA < or = 10 mM had no effect on activities of P450c17; however, VPA inhibited 3beta HSDII activity starting at 0.3 mM (reference serum unbound concentration, 0.035-0.1 mM) with an IC50 of 10.1 mM. CBZ, TPM, and LTG did not influence 3beta HSDII or P450c17 activities at typical reference serum unbound concentrations, but did inhibit 3beta HSDII and P450c17 at concentrations >10-fold higher. CONCLUSIONS: None of the tested AEDs influenced 3beta HSDII or P450c17 activities at concentrations normally used in AED therapy. However, VPA started to inhibit 3beta HSDII activity at concentrations 3 times above the typical reference serum unbound concentration. Because inhibition of 3beta HSDII activity will shift steroidogenesis toward C19 steroid production when P450c17 activities are unchanged, very high doses of VPA may promote C19 steroid biosynthesis, thus resembling PCOS. CBZ, TPM, and LTG influenced 3beta HSDII and P450c17 only at toxic concentrations.

Adrenal insufficiency attributable to adrenal hemorrhage: long-term follow-up with reference to glucocorticoid and mineralocorticoid function and replacement.

OBJECTIVE: To describe the long-term follow-up of acute adrenal insufficiency attributable to bilateral adrenal hemorrhage. METHODS: We performed a retrospective review of medical records of four patients who underwent follow-up for 6(1/2) to 19 years. RESULTS: Despite published reports of more than 500 patients with bilateral massive adrenal hemorrhage through 2001, no long-term data assessing the continuing requirements for glucocorticoid and mineralocorticoid replacement are available. After follow-up of four patients with acute bilateral adrenal hemorrhage and glucocorticoid insufficiency for 6(1/2) to 19 years, we document the absence of need for long-term mineralocorticoid replacement on the basis of no occurrence of postural hypotension, normal electrolytes, normal baseline or cosyntropin-stimulated serum aldosterone levels, and generally, though not invariably, normal plasma renin activity levels. We further document the improvement in either or both baseline and cosyntropin-stimulated serum cortisol levels in three of the four patients and the ability of one patient to function normally without cortisol replacement for 4 years. Adrenal histologic findings in this last-mentioned patient revealed previously undescribed changes consistent with regeneration and myelolipoma. Finally, we confirm bilateral atrophic adrenal glands by computed tomography 5(1/2) to 11(1/2) years after bilateral adrenal hemorrhage in three of the four patients. CONCLUSION: Long-term follow-up of patients with acute adrenal insufficiency attributable to adrenal hemorrhage demonstrates, for the first time, absence of need for prolonged mineralocorticoid replacement and some improvement in endogenous glucocorticoid function in at least some of these patients.

The control by angiotensin II of cholesterol supply for aldosterone biosynthesis.

In the adrenal glomerulosa cell, aldosterone is synthesized from cholesterol, which is supplied to the cell and stored under the form of cholesterol esters, then hydrolyzed to be transferred to the mitochondrial outer membrane and finally transported to the inner membrane where the P450 side-chain cleavage enzyme will convert it to pregnenolone. Angiotensin II (AngII), one of the major physiological regulators of mineralocorticoid synthesis, appears to affect most of the steps along this cascade and thus to exert a powerful control over the use of cholesterol for aldosterone production.

Renal inactivation, mineralocorticoid generation, and 11beta-hydroxysteroid dehydrogenase inhibition ameliorate the antimineralocorticoid effect of progesterone in vivo.

Progesterone (P) is a strong mineralocorticoid receptor (MR) antagonist in vitro. The high P concentrations seen in normal pregnancy only moderately increase renin and aldosterone concentrations. In previous in vitro studies we hypothesized that this may be explained by intrarenal conversion of P to less potent metabolites. To investigate the in vivo anti-MR potency of P, we performed an infusion study in patients with adrenal insufficiency (n = 8). They omitted 9alpha-fluorocortisol for 4 d and hydrocortisone for 0.5 d before a continuous iv infusion of aldosterone for 8.5 h, with an additional iv P infusion commenced at 4 h. During aldosterone infusions the initially elevated urinary sodium to potassium ratio decreased significantly. Despite the 1000-fold excess of P over aldosterone, the urinary sodium to potassium ratio and urinary sodium excretion increased only slightly after 3 h of P infusion. We detected inhibition of renal 11beta-hydroxysteroid dehydrogenase type 2 by P, thus giving cortisol/prednisolone access to the MR. Urinary and plasma concentrations of 17alpha-hydroxyprogesterone, a major metabolite of renal P metabolism, and those of serum androstenedione and deoxycorticosterone, a mineralocorticoid itself, increased significantly during P infusion. This supports the hypothesis of an effective protection of the MR from P by efficient extraadrenal downstream conversion of P.

Analyses of the CYP11B gene family in the guinea pig suggest the existence of a primordial CYP11B gene with aldosterone synthase activity.

In this study we describe the isolation of three genes of the CYP11B family of the guinea pig. CYP11B1 codes for the previously described 11beta-hydroxylase [Bülow, H.E.,Möbius, K., Bähr, V. & Bernhardt, R. (1996) Biochem. Biophys. Res. Commun. 221, 304-312] while CYP11B2 represents the aldosterone synthase gene. As no expression for CYP11B3 was detected this gene might represent a pseudogene. Transient transfection assays show higher substrate specificity for its proper substrate for CYP11B1 as compared to CYP11B2, which could account for the zone-specific synthesis of mineralocorticoids and glucocorticoids, respectively. Thus, CYP11B2 displayed a fourfold higher ability to perform 11beta-hydroxylation of androstenedione than CYP11B1, while this difference is diminished with the size of the C17 substituent of the substrate. Furthermore, analyses with the electron transfer protein adrenodoxin indicate differential sensitivity of CYP11B1 and CYP11B2 as well as the three hydroxylation steps catalysed by CYP11B2 to the availability of reducing equivalents. Together, both mechanisms point to novel protein intrinsic modalities to achieve tissue-specific production of mineralocorticoids and glucocorticoids in the guinea pig. In addition, we conducted phylogenetic analyses. These experiments suggest that a common CYP11B ancestor gene that possessed both 11beta-hydroxylase and aldosterone synthase activity underwent a gene duplication event before or shortly after the mammalian radiation with subsequent independent evolution of the system in different lines. Thus, a differential mineralocorticoid and glucocorticoid synthesis might be an exclusive achievement of mammals.

Disorders of mineralocorticoid synthesis.

Abnormalities of mineralocorticoid synthesis and/or metabolism profoundly affect the regulation of electrolyte and water balance and of blood pressure. Characteristic changes in extracellular potassium, sodium and hydrogen ion concentrations are usually diagnostic. Serious deficiency may be acquired, for example in Addison's disease, or inherited. In most of the inherited syndromes, the precise molecular changes in specific steroidogenic enzymes have been identified. Mineralocorticoid excess may be caused by aldosterone or 11-deoxycorticosterone by inadequate conversion of cortisol to cortisone by 11beta-hydroxysteroid dehydrogenase type 2 in target tissues (see Chapter 4), by glucocorticoid receptor deficiency or by constitutive activation of renal sodium channels. Changes in electrolyte balance and renin as well as the abnormal pattern of corticosteroid metabolism are usually diagnostic. Where these abnormalities are inherited (e.g. 11beta- or l7alpha-hydroxylase deficiencies, glucocorticoid remediable hyperaldosteronism (GRA), receptor defects, Liddle's syndrome), the molecular basis is again usually known and, in some cases, may provide the simplest diagnostic tests. Primary aldosteronism, although readily identifiable, presents problems of differential diagnosis, important because optimal treatment is different for each variant. Moreover, the mechanisms by which the variants develop are poorly understood. Finally, a significant proportion of patients with essential hypertension show characteristics of mild mineralocorticoid excess, for example low renin levels. Is this relevant to pathophysiology and, if so, is the effect induced via classic mechanisms of action or through newly discovered direct actions on the brain, heart and blood vessels? These questions are the subject of current research.

Mineralocorticoids and cardiac fibrosis: the decade in review.

1. Over the past decade, aldosterone has been shown to have direct extra-epithelial actions and substantial (patho)physiological roles in the cardiovascular system in the context of inappropriate salt status. In experimental studies on uninephrectomized rats given 0.9% NaCl solution to drink, these include blood pressure elevation via activation of circumventricular mineralocorticoid receptors in the central nervous system and production of pressure-independent cardiac hypertrophy and fibrosis by a direct effect on the heart. 2. In the Randomized Aldactone Evaluation Study (RALES) trial, patients with severe congestive heart failure (CHF) were continued on their current therapy (angiotensin-converting enzyme inhibitor, diuretic etc.) and given either placebo or spironolactone at an average dose of 26 mg/day. Mineralocorticoid receptor inhibition was accompanied by a 30% improvement in mortality and 35% less hospitalization, striking confirmation of a pathophysiological role for aldosterone in CHF. 3. Although the current basic and clinical studies are conflicting, there is evidence both for aldosterone synthesis by the failing human heart and for substantial cardiac metabolism of aldosterone. The extent to which this potential paracrine source for aldosterone may be involved in cardiac hypertrophy and cardiac fibrosis remains to be established. 4. Belatedly, aldosterone-induced proteins (e.g. serum and glucocorticoid-regulated kinase (SGK)) have been identified in epithelial mineralocorticoid target tissue. Studies are currently in progress on the cellular and molecular mechanisms involved in the coronary vasculitis provoked early in the mineralocorticoid/salt model, which, in turn, appears to trigger the subsequent perivascular and interstitial fibrotic response.

[Atrial natriuretic hormone and endocrine functions]. / Hormone natriurétique auriculaire et fonctions endocrines.

The atrial natriuretic hormone (ANP) is a cardiac hormone which gene and receptors are widely present in the body. Its main function is to lower blood pressure and to control electrolyte homeostasis. Its main targets are the kidney and the cardiovascular system but ANP interacts with many other hormones in order to regulate their secretion. The adrenal glands are the first endocrine target. Steroidogenesis, especially mineralocorticoid synthesis, is inhibited by ANP, but glucocorticoid production seems to be depressed too. As ANP synthesis is enhanced by the latter, it suggests a regulatory loop. Moreover ANP inhibits the thyroid synthesis whereas its production is enhanced by thyroid hormone. The hypothalamo-hypophyseal axis is another important target. ANP inhibits ACTH release and arginine vasopressin secretion. Vasopressin enhances ANP synthesis while GH decreases it. Finally the endocrine effects of ANP strengthen the cardiovascular and renal effects of the hormone, antagonizing the salt and water retention due to aldosterone and AVP. Because of a local production, ANP may also act as a paracrine hormone that influences the function of many endocrine systems (ovarian function for instance). In the central nervous system, ANP acts as a neurotransmitter in order to regulate pituitary and vegetative functions. Plasma ANP levels are impaired in several endocrine diseases : the plasma hormone levels increase in hypercortisolism, hyperaldosteronism, thyrotoxicosis and inappropriate antidiuretic hormone secretion; it decreases in hypothyroidism. In case of Addison's disease, ANP may be used to assess the quality of mineralocorticoid treatment, in association with the other biological criteria.