Primary Aldosteronism and Drug Resistant Hypertension: A "Chicken-Egg" Story.

Drug-resistant arterial hypertension (RH) is a major risk factor for cardiovascular disease, often due to overlooked underlying causes. Identification of such causes poses significant clinical challenges. In this setting, primary aldosteronism (PA) is a frequent cause of RH and its prevalence in RH patients is likely higher than 20%.The pathophysiological link between PA and the development and maintenance of RH involves target organ damage and the cellular and extracellular effects of aldosterone excess that promote pro-inflammatory and pro-fibrotic changes in the kidney and vasculature.The feasibility of adrenal vein sampling in PA patients with RH, and the clinical benefit achieved by adrenalectomy, further emphasize the need to implement systematic screening for this common form of secondary hypertension in the management of a high-risk population as RH patients.: We herein review the current knowledge of the factors that contribute to the RH phenotype with a focus on PA and discuss the issues regarding the screening for PA in this setting and the therapeutic approaches (surgical and medical) aimed at resolving RH caused by PA.

Serum levels of autoantibodies against the angiotensin II type I receptor are not associated with serum dicarbonyl or AGE levels in patients with an aldosterone-producing adenoma.

Patients with an aldosterone-producing adenoma (APA) carry a higher risk of cardiovascular disease and commonly have high levels of autoantibodies (AT1AA) that may activate the angiotensin II type 1 receptor (AT1R). AT1R activation is linked to an increase of the glucose metabolite methylglyoxal (MGO), a potential precursor of advanced glycation endproducts (AGEs) and driver of vascular inflammation. We investigated whether serum AT1AA levels are associated with serum MGO and AGE levels in APA patients. In a case series of 26 patients with APA we measured levels of dicarbonyls MGO, glyoxal (GO) and 3-deoxyglucosone (3-DG), and dicarbonyl-derived AGEs 5-hydro-5-methylimidazolone (MG-H1), Nε-(carboxyethyl)lysine (CEL) and Nε-(carboxymethyl)lysine (CML) with UPLC-MS/MS. We also measured AT1AA by ELISA. These measurements were repeated 1-month after adrenalectomy in a subset of 14 patients. Panels of inflammation and endothelial function were also measured by immunoassays. Although baseline higher AT1AA levels tended to be correlated with higher baseline serum MGO, GO and 3-DG levels (r = 0.18, p = 0.38; r = 0.20, p = 0.33; r = 0.23, p = 0.26; respectively), these correlations were not statistically significant. We observed no obvious correlations between higher AT1AA levels and protein-bound and free MG-H1, CEL and CML levels, and markers of inflammation and endothelial function. No decrease was observed in any of the dicarbonyls, protein-bound AGE levels and markers of inflammation and endothelial function after adrenalectomy. In patients with APA the serum levels of AT1AA were not significantly correlated with serum dicarbonyls, protein-bound and free AGE levels. Increased signalling of the AT1AA receptor may therefore be unlikely to overtly increase systemic dicarbonyl levels.

Progress in primary aldosteronism: present challenges and perspectives.

Primary Aldosteronism (PA) is a disorder of the adrenal zona glomerulosa (ZG) in which aldosterone secretion is increased and is relatively autonomous of normal regulatory mechanisms. A recent conference in Munich organized by Prof. Reincke addressed advances and challenges related to the screening, diagnosis, and identification of uni- and bilateral involvement of the diseased adrenal of PA. Some infrequently addressed issues are described herein. We postulate that most cases of PA are due to the activation by unknown mechanisms of subset of cells resulting in the formation of a multiple foci or nodules of hyperactive zona glomerulosa cells. This implies that one or several yet unidentified stimuli can drive aldosterone overproduction, as well as the proliferation of aldosterone-producing cells. Current diagnostic procedures allow to determine whether inappropriate aldosterone production is driven by one or both adrenal glands and thus to establish optimal treatment.

Oxidative stress-related proteins in a Conn's adenoma tissue. Relevance for aldosterone's prooxidative and proinflammatory activity.

BACKGROUND AND AIM: Angiotensin II (Ang II) induces oxidative stress (OxSt), which is essential for cardiovascular remodeling. Aldosterone also induces fibrosis and remodeling through direct effect on non-classical mineralocorticoid (MR) target tissues. However, studies on the role of aldosterone on OxSt and related factors in humans are lacking. MATERIALS AND METHODS: We assessed gene and protein expression of p22phox (RT-PCR and Western blot), NAD(P)H oxidase subunit essential for superoxide production and gene expression of transforming growth fator (TGF) beta, plasminogen activator inhibitor (PAI)-1, and heme oxygenase (HO)-1, effectors of OxSt (RT-PCR), in a Conn's adenoma, removed from a patient with primary hyperaldosteronism. Ang II type 1 (AT1R) and MR receptors expression were also evaluated (RT-PCR). The normal adrenal tissue adjacent to the adenoma was used as control. RESULTS: p22phox gene and protein expression were higher (31% and 53%, respectively) in the adrenal adenoma. TGFbeta, PAI-1, and HO-1 gene expression were also higher (25%, 129%, and 25%, respectively) in the adrenal adenoma while AT1R gene expression was similar (8%). The expression of MR in the adenoma was documented. CONCLUSIONS: This report demonstrates in a human model that the increased aldosterone production has effects on enzyme systems related to OxSt, enhancing the systemic fibrogenic effects of aldosterone excess through TGFbeta and PAI-1 expression which was previously demonstrated only indirectly in vitro and in animal models. The presence of MR expression in the adenoma may link the hormone with the adenoma growth. Therefore, the results of this study derived from a single case might represent an important working hypothesis for further research in a larger number of cases to clarify the role of aldosterone overproduction on OxSt and its clinical relevance.

Primary aldosteronism - part I: prevalence, screening, and selection of cases for adrenal vein sampling.

Over the last few years compelling evidence has been gathered to support the view that primary aldosteronism (PA) is far more prevalent than usually held: its prevalence rate among consecutive newly diagnosed hypertensive patients referred to hypertension centers can be as high as 11.2%. Moreover, about 4.8% of cases are a surgically curable endocrine form of hypertension, and the majority of cases do not exhibit hypokalemia at the time of clinical presentation. The impact of these results on the strategy to be used in the clinical investigation of patients with hypertension is discussed in light of novel information on the optimal screening strategy to be used for pinpointing the PA patients from the vast array of hypertensive patients.

Primary aldosteronism: part II: subtype differentiation and treatment.

After discussing in Part I (Rossi et al, J Nephrol. 2008;21:447-454) the screening strategy to identify the hypertensive patients with primary aldosteronism (PA), we report here an update on the methodology for the further diagnostic work-up and treatment of PA patients. The most common forms of PA are aldosterone-producing adenoma (APA) and adrenocortical hyperplasia (BAH), which are unilateral or bilateral sources of aldosterone excess secretion, respectively. Since APA needs a surgical approach, in contrast to BAH which requires medical treatment, it is crucial to clearly delineate a diagnostic work-up aimed at discriminating the 2 forms. Clinical usefulness and accuracy of adrenal vein sampling, imaging tests (e.g., computed tomography and magnetic resonance) and mineralocorticoid adrenocortical scintigraphy are discussed in detail.

Monozygotic twins discordant for primary aldosteronism: a case report.

This corrects the article DOI: 10.1038/jhh.2017.41.

G protein receptors 7 and 8 are expressed in human adrenocortical cells, and their endogenous ligands neuropeptides B and w enhance cortisol secretion by activating adenylate cyclase- and phospholipase C-dependent signaling cascades.

Neuropeptides B and W (NPB and NPW) are regulatory peptides that act via two subtypes of G protein-coupled receptors, named GPR7 and GPR8. RT-PCR demonstrated the expression of these receptors in both zona glomerulosa and zona fasciculata-reticularis (ZF/R) cells of the human adrenal cortex. NPB and NPW did not affect aldosterone secretion from dispersed zona glomerulosa cells but enhanced cortisol production from ZF/R cells, NPB being more effective than NPW. NPB evoked sizable cAMP and inositol triphosphate responses from ZF/R cells, which were abrogated by the adenylate cyclase inhibitor SQ-22536 and the phospholipase C inhibitor U-73122, respectively. Cortisol response to NPB was lowered by either SQ-22536 and the protein kinase (PK) A inhibitor H-89 or U-73122 and the PKC inhibitor calphostin-C and abolished by the simultaneous exposure to H-89 and calphostin-C. NPW elicited only a rise in cAMP production from dispersed ZF/R cells, and its cortisol response was suppressed by both SQ-22536 and H-89. PreproNPB and preproNPW mRNAs were detected in human adrenal cortexes. We conclude that: 1) NPB and NPW exert a secretagogue action on human ZF/R cells, probably acting in an autocrine-paracrine manner; and 2) the effect of NPB is mediated by both the adenylate cyclase/PKA and the phospholipase C/PKC cascades, whereas that of NPW involves only the activation of the former signaling pathway.

Reciprocal regulation of endothelin-1 and nitric oxide: relevance in the physiology and pathology of the cardiovascular system.

The endothelium plays a crucial role in the regulation of cardiovascular structure and function by releasing several mediators in response to biochemical and physical stimuli. These mediators are grouped into two classes: (1) endothelium-derived constricting factors (EDCFs) and (2) endothelium-derived relaxing factors (EDRFs), the roles of which are considered to be detrimental and beneficial, respectively. Endothelin-1 (ET-1) and nitric oxide (NO) are the prototypes of EDCFs and EDRFs, respectively, and their effects on the cardiovascular system have been studied in depth. Numerous conditions characterized by an impaired availability of NO have been found to be associated with enhanced synthesis of ET-1, and vice versa, thereby suggesting that these two factors have a reciprocal regulation. Experimental studies have provided evidence that ET-1 may exert a bidirectional effect by either enhancing NO production via ETB receptors located in endothelial cells or blunting it via ETA receptors prevalently located in the vascular smooth muscle cells. Conversely, NO was found to inhibit ET-1 synthesis in different cell types. In vitro and in vivo studies have started to unravel the molecular mechanisms involved in this complex interaction. It has been clarified that several factors affect in opposite directions the transcription of preproET-1 and NO-synthase genes, nuclear factor-KB and peroxisome proliferator-activated receptors playing a key role in these regulatory mechanisms. ET-1 and NO interplay seems to have a great relevance in the physiological regulation of vascular tone and blood pressure, as well as in vascular remodeling. Moreover, an imbalance between ET-1 and NO systems may underly the mechanisms involved in the pathogenesis of systemic and pulmonary hypertension and atherosclerosis.

The role of endothelins in the paracrine control of the secretion and growth of the adrenal cortex.

Endothelins (ETs) are a family of vasoactive peptides (ET-1, ET-2, and ET-3) mainly secreted by vascular endothelium and widely distributed in the various body systems, where they play major autocrine/paracrine regulatory functions, acting via two subtypes of receptors (ETA and ETB): Adrenal cortex synthesizes and releases ETS and expresses both ETA and ETB. Zona glomerulosa possesses both ETA and ETB, whereas zona fasciculata/reticularis is almost exclusively provided with ETB. ETS exert a strong mineralocorticoid and a less intense glucocorticoid secretagogue action, mainly via ETB receptors. ETS also appear to enhance the growth and steroidogenic capacity of zona glomerulosa and to stimulate its proliferative activity. This trophic action of ETS is likely to be mediated mainly by ETA receptors. The intraadrenal release of ETS undergoes a multiple regulation, with the rise in blood flow rate and the local release of nitric oxide being the main stimulatory factors. Data are also available that indicate that ETS may also have a role in the pathophysiology of primary aldosteronism caused by adrenal adenomas and carcinomas.

Homocysteine-lowering treatment in coronary heart disease.

Homocysteine (Hcy) is a sulphur-containing amino acid product of methionine's metabolism. Hyperhomocysteinemia (HHcy) is considered an independent risk factor for cardiovascular (CV) disease, at least in high-risk patients. In fact, evidence indicates that although mild HHcy may be regarded as a minor risk factor for CHD in low-risk patients, it can play a role in triggering new events in patients with known CHD, also by interacting with the "classical" CV risk factors. This is of much interest because HHcy represents a correctable risk factor, inasmuch vitamin supplementation as has been shown to effectively lower total homocysteine plasma levels (tHcy). While case-control and cross-sectional studies have consistently demonstrated an association of HHcy with CV disease, prospective studies have given conflicting results. Moreover, the effect of the homocysteine-lowering treatment in preventing CV events is still under debate. Thus, it remains unclear which patients should be screened for HHcy and which ones should be treated to lower tHcy. In this paper we shall report and discuss knowledge on the potential role of HHcy in the development of CHD and on the benefits due to tHcy-lowering treatment with vitamins.

Interactions between endothelin-1 and the renin-angiotensin-aldosterone system.

The renin-angiotensin-aldosterone (RAA) system and the endothelin (ET) system entail the most potent vasopressor mechanisms identified to date. Although they were studied in depth in relation to arterial hypertension and cardiovascular diseases, limited information on their interrelationships in causing hypertension and related target organ damage exists. The identification of consensus sequences for jun in the regulatory region of the preproendothelin-1 (ppET-1) gene raised the possibility of its transcriptional regulation by angiotensin II (Ang II). This was confirmed by the finding that stimulation with Ang II of cultured vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) induced expression of the ppET-1 gene and synthesis of ET-1. Endogenously produced ET-1 was found to contribute to the hypertrophic response of cardiomyocytes to Ang II and thereby to cardiac hypertrophy. Furthermore, ET-1 exerts multifaceted effects on the RAA system, such as dose-dependent inhibition of renin synthesis, and stimulation of aldosterone secretion. The finding of abundant specific ET-1 receptors in the adrenocortical zona glomerulosa (ZG) suggested a direct secretagogue effect of ET-1. In rats, ETB receptors mediate such an effect, whilst in humans, both ETA and ETB receptor subtypes intervene in regulating the transcription of the aldosterone synthase gene. In addition, ET-1 stimulates DNA synthesis and proliferation of ZG cells via ETA receptors and, therefore, might play a role in cell turnover of the normal adrenal cortex and in the onset of adrenal tumours. Studies on the in vivo interactions between ETs and the RAA system have given conflicting results, insofar as some suggested a participation of ET-1 in the pressor and cellular effects of exogenously administered Ang II, whereas others did not in the transgenic TGR(Ren 2m)27 rats and in the two-kidney, one clip.

Characterisation of sleep disturbances in postural orthostatic tachycardia syndrome: a polysomnography-based study.

BACKGROUND AND AIM: Postural orthostatic tachycardia syndrome (PoTS) has been frequently associated with sleep disturbances but objective sleep data are lacking. In addition, although regional autonomic denervation has been described, less is known about autonomic nervous activity overnight in these patients. PATIENTS/METHODS: A full polysomnography and heart rate variability were performed on 37 patients diagnosed with PoTS . In addition, a multiple sleep latency test (MSLT) was conducted on a subgroup of patients with excessive daytime sleepiness. RESULTS: The polysomnographic data did not show major pathological findings except the percentage spent in rapid eye movement (REM) sleep which was slightly reduced at 18.4%. The MSLT did not confirm excessive daytime sleepiness as median mean sleep latency was 14.4 min (11.8-17.5). When comparing patients with and without subjective daytime sleepiness, it was found that the latter had a reduced parasympathetic activation at night as expressed by the average high frequency [6936.5 ms(2) (6028.2-8675.5) vs. 4689.5 (3922.7-7685.2) p < 0.05]. CONCLUSION: Patients with PoTS do not exhibit polysomnographic findings consistent with relevant sleep pathologies nor objective daytime sleepiness. Subjective daytime sleepiness is associated with enhanced activation of the parasympathetic nervous system.

Endothelins stimulate deoxyribonucleic acid synthesis and cell proliferation in rat adrenal zona glomerulosa, acting through an endothelin A receptor coupled with protein kinase C- and tyrosine kinase-dependent signaling pathways.

The effects of endothelins (ET) on the proliferative activity of the rat adrenal cortex have been investigated in vivo, using an in situ perfusion technique of the intact left gland. The chemicals were dissolved in the perfusion medium, and the perfusion continued for 120 min. ET-1 concentration dependently increased the mitotic index and [3H]thymidine incorporation into DNA in the zona glomerulosa (ZG; 6- and 3-fold increases, respectively, at a 10(-8) M concentration), but not in the inner adrenocortical layers, where the basal proliferative activity was negligible. The effect of 10(-8) M ET-1 was blocked by the ETA receptor antagonist BQ-123, whereas the ETB receptor antagonist BQ-788 was ineffective. ET-2 and ET-3 (10(-8) M) enhanced DNA synthesis in the ZG, but their effects were less intense than that of 10(-8) M ET-1 and were directly related to their binding potency for the ETA receptor subtype (ET-1 > ET-2 >> ET-3). The selective ETB receptor agonists BQ-3020, IRL-1620, and sarafotoxin-6B were ineffective. The ZG proliferogenic action of 10(-8) M ET-1 was reversed by both the protein kinase C inhibitor Ro31-8220 and the tyrosine kinase inhibitor tyrphostin-23; a complete blockade was obtained at a 10(-6)-M concentration of each inhibitor. In contrast, neither the protein kinase A inhibitor H-89 (10(-5) M) nor the cyclooxygenase and lipoxygenase inhibitors indomethacin and phenidone (10(-5) M) affected ET-1 action. Collectively, our findings indicate that ETs stimulate the proliferation of rat adrenal ZG cells, acting through ETA receptors coupled with protein kinase C- and tyrosine kinase-dependent signaling pathways. The results of the present study are in keeping with the view that in mammals, ZG is the proliferative layer involved in the maintenance of growth of the entire adrenal cortex and with the previous autoradiographic demonstration that ZG is the only adrenocortical layer provided with ETA receptors.

Autocrine-paracrine role of endothelin-1 in the regulation of aldosterone synthase expression and intracellular Ca2+ in human adrenocortical carcinoma NCI-H295 cells.

The role played by endothelin (ET-1) and its receptor subtypes A and B (ET(A) and ET(B)) in the functional regulation of human NCI-H295 adrenocortical carcinoma cells has been investigated. Reverse transcription-PCR with primers specific for prepro-ET-1, human ET-1 converting enzyme-1, ET(A), and ET(B) complementary DNAs consistently demonstrated the expression of all genes in NCI-H295 cells. The presence of mature ET-1 and both its receptor subtypes was confirmed by immunocytochemistry and autoradiography, respectively. Aldosterone synthase (AS) messenger RNA was also detected in NCI-H295 cells, and AS gene expression was enhanced by both ET-1 and the specific ET(B) agonist IRL-1620; this effect was not inhibited by either the ET(A) antagonist BQ-123 or the ET(B) antagonist BQ-788. A clear-cut increase in the intracellular Ca2+ concentration in NCI-H295 cells in response to ET(B), but not ET(A), activation was observed. In light of these findings, the following conclusions can be drawn: 1) NCI-H295 cells possess an active ET-1 biosynthetic pathway and are provided with ET(A) and ET(B) receptors; 2) ET-1 regulates in an autocrine/paracrine fashion the secretion of aldosterone by NCI-H295 cells by enhancing both AS transcription and raising the intracellular Ca2+ concentration; and 3) the former effect of ET-1 probably involves the activation of both receptor subtypes, whereas calcium response is exclusively mediated by the ET(B) receptor.

Pituitary adenylate-cyclase activating peptide enhances aldosterone secretion of human adrenal gland: evidence for an indirect mechanism, probably involving the local release of catecholamines.

Evidence is accumulating that the adrenal medulla exerts a paracrine control on the secretory activity of the cortex by releasing catecholamines and several regulatory peptides. Pituitary adenylate-cyclase activating peptide (PACAP) is contained in the adrenal medulla of several mammalian species and in human pheochromocytomas. Thus, we investigated whether PACAP exerts a modulatory action on steroid secretion by the human adrenal cortex in vitro. Adrenal slices (including both capsule and medulla) and dispersed adrenocortical cells (obtained from the gland tail deprived of medulla) were employed. Both adrenal preparations secreted aldosterone (ALDO) and cortisol in response to 10 nmol/L ACTH. PACAP (10 nmol/L) was found to enhance basal ALDO production by adrenal slices, but not by dispersed cells. PACAP was ineffective on cortisol secretion of both preparations. Adrenal slices displayed a marked ALDO, but not cortisol, secretory response to 100 nmol/L isoprenaline or noradrenaline. l-Alprenolol (1 mumol/L), a specific beta-adrenoceptor antagonist, completely suppressed the ALDO response to both beta-adrenoceptor agonists and 10 nmol/L PACAP, without per se altering basal ALDO output by adrenal slices. PACAP (10 nmol/L) induced a net rise in catecholamine release by adrenal slices. Taken together, our present findings suggest that PACAP indirectly stimulates ALDO secretion by the human adrenal cortex, probably by eliciting the local release of catecholamines by medullary chromaffin cells that are also scattered in the cortical tissue, especially the zona glomerulosa.

Changes in left ventricular anatomy and function in hypertension and primary aldosteronism.

We investigated the effects on the heart of hypertension due to the excess of aldosterone and suppression of the renin-angiotensin system caused by primary aldosteronism with M-mode echocardiography and transmitral Doppler flow velocity measurements. We studied 34 consecutive patients with primary aldosteronism and 34 with essential hypertension individually matched for age, gender, race, body mass index, blood pressure values, and duration of hypertension. The groups were similar in age, body mass index, blood pressure, and duration of hypertension. However, lower serum potassium levels (3.5 +/- 0.6 versus 4.1 +/- 0.2 mmol/L, P < .0001) and plasma renin activity (0.53 +/- 0.45 versus 1.82 +/- 1.59 ng Ang I x mL-1 x h-1, P < .0001) and higher plasma aldosterone levels (1107 +/- 774 versus 206 +/- 99 pmol/L, P < .0001), left ventricular wall thickness, and left ventricular mass index (112 +/- 4.7 versus 98 +/- 3.7 g/m2, P = .029) were found in patients with primary aldosteronism compared with those with essential hypertension. Similarly, the PQ interval was longer (173 +/- 20 versus 141 +/- 14 milliseconds, P < .001) in primary aldosteronism than in essential hypertension patients. Significantly more primary aldosteronism than essential hypertension patients had left ventricular hypertrophy or left ventricular concentric remodeling (50% versus 15%, chi 2 = 11.97, P = .007). Both the E wave flow velocity integral (1063 +/- 65 versus 1323 +/- 78, P = .013) and the E/A integral ratio (0.91 +/- 0.05 versus 1.25 +/- 0.08, P < .001) were lower, and atrial contribution to left ventricular filling was higher (53.3 +/- 1.5% versus 45.5 +/- 1.3% P < .001) in patients with primary aldosteronism compared with essential hypertension patients. After 1 year of follow-up, highly significant decreases of left ventricular wall thickness and mass were observed in patients treated with surgical excision of an aldosterone-producing tumor, but not in those with medical therapy. Thus, in patients with primary aldosteronism, the excess aldosterone with suppression of the renin-angiotensin system is associated with both increased left ventricular mass and significant changes of left ventricular diastolic filling. The former changes appear to be reversible on removal of the cause of excessive aldosterone production.

Endothelin adrenocortical secretagogue effect is mediated by the B receptor in rats.

We investigated the gene expression and localization of endothelin-1 (ET-1) receptor subtypes ET(A) and ET(B) in the rat adrenal cortex as well as their involvement in the corticosteroid secretagogue effect of ET-1 in vitro. Reverse transcription-polymerase chain reaction with primers specific for ET(A) and ET(B) cDNAs demonstrated the expression of both receptor genes in homogenates of adrenocortical tissue. However, in isolated zona glomerulosa and zona fasciculata cells, only ET(B) mRNA was detected. Autoradiographic examination of the selective displacement of 125I-ET-1 binding by BQ-123 and BQ-788 (specific ligands for ET(A) and ET(B), respectively) indicated that zona glomerulosa possesses both ET(A) and ET(B), whereas zona fasciculata is exclusively provided with ET(B). ET-1 enhanced in a concentration-dependent manner aldosterone and corticosterone secretions of dispersed zona glomerulosa and zona fasciculata cells, respectively. The ET(B) antagonist BQ-788 markedly reduced the secretory response of zona glomerulosa cells and completely suppressed that of zona fasciculata cells, whereas the ET(A) antagonist BQ-123 was ineffective. These findings indicate that in the rat, the adrenocortical secretagogue action of ET-1 is mediated by the ET(B) receptor subtype and that the ET(A) receptor is not directly involved in such an effect.

Effects of adrenomedullin on the human adrenal glands: an in vitro study.

Numerous lines of evidence indicate that adrenal medulla exerts a paracrine control on the secretory activity of the cortex by releasing catecholamines and several regulatory peptides. Adrenomedullin (ADM) is contained in adrenal medulla of several mammalian species, including humans. Thus, we investigated whether human ADM1-52 exerts a modulatory action on steroid secretion of human adrenal cortex in vitro. Dispersed adrenocortical cells (obtained from the gland tail deprived of chromaffin cells) and adrenal slices (including both capsule and medulla) were employed. ADM specifically inhibited angiotensin II-stimulated aldosterone secretion of dispersed cells and enhanced basal aldosterone production by adrenal slices, minimal effective concentrations being 10(-7) and 10(-9) mol/L, respectively. These effects of ADM were suppressed by the CGRP1 receptor antagonist CGRP8-37 (10(-5) mol/L). Neither basal and ACTH-stimulated aldosterone secretion of dispersed cells nor agonist-enhanced aldosterone production by adrenal slices were affected by ADM, which also did not alter cortisol secretion of both types of adrenal preparations. ADM (10(-6) mol/L) blunted the aldosterone secretagogue action of the Ca2+ ionophore A23187 (10(-5) mol/L) on dispersed cells and adrenal slices. The beta-adrenoceptor antagonist l-alprenolol (10(-6) mol/L) suppressed aldosterone response of adrenal slices to 10(-7) mol/L isoprenaline and ADM. ADM concentration dependently raised epinephrine and norepinephrine release by adrenal slices, minimal effective concentration being 10(-9) mol/L. Collectively, these findings suggest that ADM, acting via the CGRP1 receptor subtype, exerts a direct inhibitory effect on angiotensin II-stimulated aldosterone secretion, which, when the integrity of adrenal tissue is preserved, is overcome and reversed by an indirect stimulatory action, conceivably involving the release of catecholamines by adrenal chromaffin cells.