Two-dimensional, M-mode and Doppler-derived echocardiographic parameters in sedated healthy growing female sheep.

Despite the fact that sheep are a widely used animal model in cardiovascular research, reference values for transthoracic echocardiography in normal growing animals are not available. Eight healthy female lambs underwent two-dimensional, M-mode and pulsed wave Doppler echocardiographic examination at 100 days of age and every three months thereafter over a 12-month period. The study was conducted under sedation with midazolam, butorphanol and constant rate infusion of intravenous propofol. Their growth phase was completed at about one year of age. All the echocardiographic parameters considered were significantly correlated with body weight and age class except for the left ventricular systolic and diastolic diameters. Functional indices were not correlated to body weight or age except for the E-point to septal separation distance (EPSS). Doppler-derived parameters were not influenced by independent variables. Transthoracic echocardiography can be considered an applicable method for cardiovascular research using a growing lamb animal model after appropriate adjustments for age and body size.

Blood pressure control has distinct effects on executive function, attention, memory and markers of cerebrovascular damage.

Hypertension causes cognitive impairment, involving mainly executive functions, but the effect of blood pressure (BP) control on the different cognitive domains is still debated. We correlated executive function, attention and memory with BP control and cerebrovascular damage in 60 undemented middle-aged hypertensives at baseline and after 6-year follow-up. At first evaluation, the patients with poor BP control had higher score of white matter lesions, reduced cerebrovascular reserve capacity and greater carotid intima-media thickness (IMT) than those with good BP control. Performance on executive tests correlated with IMT and with performance on attention tests, which was impaired by low diastolic BP. At long-term follow-up, performance in attention and executive tests improved in spite of the minor improvement of BP control, increased IMT and worse memory. Low diastolic BP has a negative effect on attention, which affects executive performance at first cross-sectional examination. This confounding effect has to be taken into consideration when planning studies on cognitive function. Longitudinal studies are required to unravel the effect of BP control on cognitive function, as only long-term antihypertensive treatment improves both attention and executive performance.

High angiotensin II state without cardiac remodeling (Bartter's and Gitelman's syndromes): are angiotensin II type 2 receptors involved?

BACKGROUND/AIMS: While Angiotensin II (Ang II) is a major factor in the development of cardiomyocyte hypertrophy and a pivotal role for Ang II signals via ERK1/2 has been identified, mechanism(s) responsible are still unclear. As Bartter's and Gitelman's syndrome patients (BS/GS) have increased Ang II, and yet normo/hypotension, hyporesponsiveness to pressors and blunted Ang II signaling via type 1 receptors (AT1R), this study assesses BS/GS's left ventricular (LV) mass and structure as well as Ang II induced ERK1/2 phosphorylation compared with essential hypertensive patients (EH) and normotensive healthy subjects (C) to gain insight into Ang II mediated processes. METHODS: Indices of cardiac hypertrophy were determined by M-mode, two-dimensional echo Doppler and ERK phosphorylation by Western blot. RESULTS: None of BS/GS exhibited LV remodelling; LV mass, LV end-diastolic volume and mass/volume ratio were unchanged vs C (60+/-14 g/m2 vs 64+/-12, 64+/-12 ml/m2 vs 60+/-8 and 0.95+/-0.2 vs 1.0+/-0.2, respectively) and reduced vs EH (119+/-15, p<0.001, 78+/-9, p<0.05 and 1.52+/-0.15, p<0.01). Despite BS/GS's higher plasma renin activity and aldosterone and unchanged level of AT1R, Ang II induced ERK1/2 phosphorylation was reduced vs both C and EH: 0.64 d.u.+/-0.08 vs 0.90+/-0.06 in C, p<0.006, and vs 1.45+/-0.07 in EH, p<0.001. CONCLUSION: The data point to a direct cardioremodeling role for Ang II and support a role of Ang II type 2 receptor (AT2R) signaling as involved in the lack of cardiovascular remodeling in BS/GS. However, further studies using more direct approaches to demonstrate the effects of AT2R signaling must be pursued.

Fibrinogen kinetics and protein turnover in hypertension: Effects of insulin.

BACKGROUND AND AIM: Hyperfibrinogenemia, a cardiovascular risk factor, is frequent in hypertension and largely unexplained. In this study, we measured fibrinogen production and whole-body protein turnover under both basal and hyperinsulinemic states, in hypertensive [H] and control [C] subjects, using a leucine stable isotope tracer and precursor-product relationships. METHODS AND RESULTS: Since hypertension is often a feature of the "metabolic", insulin resistance syndrome, which in turn affects both fibrinogen kinetics and whole-body protein turnover, we selected hypertensive subjects without the metabolic syndrome. Following basal measurements, an euglycemic, approximately euaminoacidemic, hyperinsulinemic clamp was performed, with plasma insulin raised to 700-900 pmol/L. In H, rates of the fractional and absolute synthesis (FSR and ASR, respectively) of fibrinogen were 30%-40% greater (p<0.05 or less) than in C in both states, whereas leucine turnover was normal. Hyperinsulinemia did not modify fibrinogen synthesis in either group with respect to baseline, whereas it suppressed leucine appearance from endogenous proteolysis by approximately 40% to same extent in both groups. Amino acid clearance was similar in both the H and C subjects. In H, the insulin-mediated glucose disposal (M) was approximately 25% lower, (although insignificantly) than in controls, showing no overall insulin resistance. There was an inverse correlation between M and fibrinogen FSR during the clamp. CONCLUSIONS: In essential hypertension fibrinogen production is increased, is not further stimulated by insulin, and is inversely related to insulin sensitivity at high-physiological insulin concentrations. Amino acid disposal and basal as well as insulin-responsive protein degradation rates are instead normal.

Intravenous thrombolysis in the emergency department for the treatment of acute ischaemic stroke.

BACKGROUND AND AIMS: Thrombolytic therapy with intravenous recombinant tissue plasminogen activator (rt-PA) improves outcome in patients with ischaemic stroke treated within 3 h of symptom onset, but its extended implementation is limited. A pilot study was designed to verify whether evaluation of patients with acute ischaemic stroke and their treatment with intravenous rt-PA in the emergency department (ED), followed by transportation to a semi-intensive stroke care unit, offers a safe and effective organisational solution to provide intravenous thrombolysis to acute stroke patients when a stroke unit (SU) is not available. METHODS: After checking for inclusion and exclusion criteria, ED doctors contacted the stroke team with a single page, located family members and urgently obtained computed tomography scan and laboratory tests. A stroke team investigator clinically assessed the patient, obtained written informed consent and supervised intravenous rt-PA in the ED. After treatment, the patient was transferred to the SU for rehabilitation and treatment of complications, under supervision of the same stroke team investigator. RESULTS: 52 patients were treated with intravenous rt-PA within 3 h of symptom onset. 20 patients (38%) improved neurologically after 24 h, the number increased to 30 (58%) after one week. At 3 months 22 patients had a favourable outcome (43%). The 3-month mortality rate was 12%. Symptomatic cerebral haemorrhage was observed in two patients (4%). CONCLUSIONS: Intravenous rt-PA administration in the ED is an effective organisational solution for acute ischaemic stroke when an SU is not established.

Effect of doxazosin on oxidative stress related proteins in essential hypertensive patients.

The role of oxidative stress in the pathophysiology of hypertension has stimulated the investigation of strategies to reduce oxidative stress via antioxidant defenses. Using a molecular biology approach, we report, in essential hypertensive patients, the effect of doxazosin treatment on the mononuclear cell gene and protein expression of two major elements in the oxidative stress and vascular remodeling-related pathways: p22(phox) and PAI-1. Ten essential hypertensive patients were treated with Doxazosin (4 mg/day) for two weeks (EH + D) and compared with ten untreated hypertensive patients (EH) and ten normotensive subjects (C). In EH p22(phox) and PAI-1 mRNA and protein level was increased compared with C. In EH + D, doxazosin reduced p22(phox) and PAI-1 gene and protein expression, which was similar to that of C. These results demonstrate for doxazosin an inhibitory effect on oxidative stress related proteins at gene and protein level, which confirms at molecular level a powerful antioxidant potential for this agent that could translate, in the long term, into a powerful antiatherosclerotic effect.

Comparison between nifedipine and carvedilol in the treatment of de novo arterial hypertension after liver transplantation: preliminary results of a controlled clinical trial.

There is no controlled clinical trial on the treatment of de novo arterial hypertension after liver transplantation (LT) a common complication using calcineurin inhibitors (CNI) for immunosuppressive therapy. The aim of this study was to compare the efficacy and safety of nifedipine, a calcium channel blocker, and carvedilol, an alpha1- and beta-blocker. The study included 50 patients who developed arterial hypertension after LT. The data on the first 30 patients who have completed 12-month follow-up are reported herein. Eighteen patients received nifedipine, and 12 patients received carvedilol. Patients were evaluated monthly at the outpatient clinic for 1 year. If patients developed severe adverse effects to nifedipine, they were switched to carvedilol and vice versa (therapy failure). The two groups were similar for clinical features, indications for LT, immunosuppressive therapy, and baseline blood pressures. A failure of treatment was observed in 9 of 18 patients treated with nifedipine (50.0%) and one of 12 patients treated with carvedilol (8%, P < .025). Nifedipine was effective in 4 of 18 patients, carvedilol, in 4 of 12 patients (22.21% vs 33.3%, P = NS). Two of the nine nonresponders to nifedipine responded to carvedilol. The efficacy of monotherapy was observed in 11 of 40 randomized patients (27.5%). Carvedilol monotherapy is as effective as nifedipine but far better tolerated.

Effect of epoetin on HO-1 mRNA level and plasma antioxidants in hemodialysis patients.

OBJECTIVE: Patients with renal failure and undergoing hemo- (HD) or peritoneal dialysis are under oxidative stress which is thought to contribute to the long-term complications noted in this patient population. One effect of HD-induced oxidative stress is via red blood cell (RBC) membrane lipid peroxidation leading to RBC destruction and anemia. Interaction of this oxidative stress with epoetin (EPO) treatment to increase RBC number and Hb concentration remains unexplored. PATIENTS AND METHODS: This preliminary study used RT-PCR as well as colorimetric based assay approaches to evaluate the effect of EPO-alpha treatment on markers of oxidative stress in hemodialysis patients. Eighteen patients (12 males, 6 females, age range 45 - 68), were treated with EPO-alpha (Eprex) 50 UI/kg thrice weekly over an 8-month study period. Monocytes were isolated at baseline, then monthly thereafter, monocyte heme-oxygenase-1 (HO-1) and plasma Hb and antioxidant power (AOP) were determined. RESULTS AND CONCLUSIONS: Treatment with EPO increased Hb (9.4 +/- 0.7 g/dl to 10.9 +/- 0.5, mean +/- SD p < 0.001). In addition, both monocyte HO-1 mRNA (0.34 +/- 0.08 vs. 0.59 +/- 0.02 d.u. p < 0.001) and plasma AOP (1,379.8 +/- 175 micromol/l to 1,624 +/- 170, p < 0.04) increased. While AOP changes showed no correlation with other indices, increases in HO-1 and Hb were positively correlated using 2 different measures: delta Hb (peak Hb - baseline Hb) vs. delta HO-1 (peak HO-1 mRNA - baseline HO-1 mRNA) as well as delta Hb(5 months-baseline) vs. delta HO-1 (5 months - baseline) mRNA (r = 0.81, p < 0.001 and r = 0.76, p < 0.001; respectively). In conclusion, the increases upon EPO treatment of both HO-1 gene expression and plasma AOP as well as the significant correlation between delta Hb and delta HO-1 mRNA suggest that EPO treatment reduces oxidative stress via a combination of effects. These could potentially include effects on oxidative stress directly as well as effects on the levels and types of antioxidants present in plasma.

Oxidative stress and TGFbeta in kidney-transplanted patients with cyclosporin-induced hypertension. Effect of carvedilol and nifedipine.

Cyclosporin is a powerful stimulator of oxidative stress signaling, leading to TGFbeta production, NO degradation, endothelial dysfunction, hypertension and post-transplant nephropathy. Carvedilol, alpha1-beta-blocker with strong antioxidant activity, may interfere with this chain of events. Therefore, we measured monocyte ecNOS, TGFbeta and heme oxygenase-1 (HO-1) mRNA level and plasma nitrite/nitrate, 3-nitrotyrosine, an estimate of peroxynitrite, and total plasma antioxidant power in kidney-transplanted patients with post-transplant hypertension, before and after treatment with carvedilol, 25 - 50 mg o.d. orally for 4 months (n = 15). The dihydropyridine calcium channel blocker nifedipine (n = 10) was used as comparator antihypertensive drug. Blood pressure fell to a similar extent with both drugs. Carvedilol increased plasma antioxidant power and HO-1 mRNA and reduced 3-nitrotyrosine and TGFbeta mRNA levels, while the same was not observed with nifedipine. Monocyte ec NOS mRNA levels and plasma nitrite/nitrate were higher in the patients than in a normotensive healthy control group and were unaffected by either treatment. In conclusion, carvedilol reduces the oxidative stress and corrects the altered cellular signaling mediated by oxidative stress in CsA-induced post-transplant hypertension. Therefore, it may prevent long-term complications, such as endothelial dysfunction, fibrogenesis and post-transplant nephropathy by decreasing NO degradation and production of TGFbeta, a key fibrogenic cytokine, and by activating HO-1 production.

Increased red cell sodium-lithium countertransport and lymphocyte cytosolic calcium are separate phenotypes in patients with essential hypertension.

Increased red blood cell sodium-lithium countertransport (SLC) activity and elevated intracellular calcium have been observed in hypertensive patients. The association of these ion transport abnormalities with each other and with another phenotype, insulin resistance, has been suggested. We investigated whether elevated SLC activity and increased lymphocyte cytosolic calcium (Ca(cyt)) occur in the same individuals and whether either is associated with hyperinsulinaemia. We measured SLC activity, lymphocyte Ca(cyt)and fasting insulin levels in hypertensive patients and normal subjects. Consistent with prior studies, SLC activity was significantly and positively correlated with fasting insulin levels (r = 0.45, P < 0.01). However, SLC activity and lymphocyte Ca(cyt) were significantly but inversely correlated (r = -0.42, P < 0.01) and lymphocyte Ca(cyt) was also inversely correlated with fasting insulin (r = -0.55, P < 0.001). When the study participants were instead separated into two groups based on fasting insulin levels, those above the median (15 microU/ml) had significantly higher SLC activity and significantly lower Ca(cyt). When separated by lymphocyte Ca(cyt) levels (above or below 120 nM) those patients with low lymphocyte Ca(cyt) had significantly higher SLC activity and significantly higher insulin levels. Multiple linear regression showed that fasting insulin was significantly predictive of SLC activity (P = 0.05) and Ca(cyt) (P < 0.01). Thus, elevated SLC activity and increased lymphocyte Ca(cyt) are separate and distinct ion transport phenotypes in hypertensive patients, linked through a relationship to hyperinsulinaemia that is direct with SLC activity and inverse with lymphocyte Ca(cyt).

[Arterial hypertension and oxidative stress induced by cyclosporin. Effect of carvedilol]. / Ipertensione arteriosa e stress ossidativo indotti dalla ciclosporina. Effetto del carvedilolo.

Cyclosporin-induced hypertension and endothelial dysfunction have been attributed to the effects of cyclosporin on factors controlling vasomotor tone. Endothelial nitric oxide (NO) regulates basal vasodilation, and an NO-mediated protective mechanism from cyclosporin-induced vasoconstriction has been proposed. In transplanted patients with cyclosporin-induced hypertension, we have recently demonstrated upregulation of the NO system and superoxide and free radical overproduction, which, by increasing NO metabolism, could induce hypertension, vascular remodeling and chronic rejection. In the present work, we have evaluated endothelial constitutive NO synthase (ecNOS), transforming growth factor beta and heme oxygenase-1 (protective against oxidative stress), mRNA production and plasma NO metabolites, peroxynitrite and antioxidant power in 15 kidney transplanted patients before and after 4 months of treatment with carvedilol alpha 1-beta-blocker and potent antioxidant. Our aim was to study the efficacy of the reduction of oxidative stress on complications such as endothelial dysfunction and fibrogenesis. Monocyte ecNOS and plasma NO metabolites remained higher versus those of control subjects and were unchanged by carvedilol, while antioxidant power and heme oxygenase-1 mRNA production increased. Peroxynitrite, as well as transforming growth factor beta mRNA, were reduced by carvedilol. It also normalized blood pressure. In conclusion, carvedilol reduces oxidative stress and normalizes blood pressure; ecNOS remains upregulated while mRNA for transforming growth factor beta, a key fibrogenic cytokine, is reduced by carvedilol, which seems to preserve protective mechanisms such as NO and heme oxygenase-1 against long-term complications of oxidative stress, e.g., endothelial dysfunction, fibrogenesis and chronic rejection.

Abnormalities of Gq-mediated cell signaling in Bartter and Gitelman syndromes.

BACKGROUND: The constitutive endothelial isoform of nitric oxide synthase (ecNOS) and nitric oxide (NO) production are increased in patients with Bartter syndrome (BS) and Gitelman (GS) syndrome and may reduce vascular tone. Moreover, these patients present an abnormal cell signaling [reduced stimulated intracellular calcium ([Ca(2+)](i)) and inositol-1,4,5,triphosphate ([IP(3)](i)) in neutrophils], suggesting the presence of a generalized reduction of protein kinase C (PKC) and cell reactivity. Since PKC regulates ecNOS gene expression, we evaluated the signal transduction system involving Gq protein, PKC, and ecNOS in circulating nucleated cells from patients with BS/GS. METHODS: Nucleated blood cells from 2 BS and 7 GS and from 10 controls (C) were used. PKC activity was evaluated in neutrophils by radioenzymatic assay; PKC alpha concentration was evaluated in monocytes by Western blot analysis. ecNOS and G alpha q mRNA production was evaluated in monocytes by reverse transcription-polymerase chain reaction (RT-PCR) analysis using specific primers and quantitated by PCR-based semiquantitative analysis of ecNOS and G alpha q mRNA expression. RESULTS: Cytosol and membrane basal PKC activity were similar in neutrophils from BS/GS and C (70 +/- 3 vs. 80 +/- 2; 37 +/- 3 vs. 46 +/- 2 pmol/min/mg protein, respectively), while fMLP-stimulated membrane PKC activity increased to a lower extent in BS/GS (from 43 +/- 2 to 53 +/- 3 vs. 38 +/- 2 to 66 +/- 3 pmol/min/mg protein, P < 0.05 for the difference). Membrane PKC alpha expression was similar in basal conditions (8.5 +/- 1.5 vs. 12.4 +/- 4.0 densitometric units), but increased after fMLP was reduced in BS/GS (4.5 +/- 1.4 vs. 9.5 +/- 2.1, P < 0.01). In BS/GS, PKC stimulation with PMA dose dependently reduced ecNOS gene expression (from 0.80 +/- 0.05 to 0.78 +/- 0.03 densitometric units; PMA 50 nmol/L, P = NS; to 0.55 +/- 0.07, PMA 100 nmol/L, P < 0.001) to an undetectable expression (PMA 200 nmol/L). Qualitatively similar effects were seen in monocytes from control subjects. Incubation of monocytes from patients and controls with the PKC inhibitor GF109203X increased ecNOS mRNA, with no difference between patients and controls. G alpha q mRNA was reduced in BS/GS versus controls (0.87 +/- 0.013 vs. 0.98 +/- 0.005 densitometric units, P < 0.0004). CONCLUSION: An abnormal G alpha q expression blunts cell signaling and PKC production in BS/GS. A reduced PKC up-regulated NO system may contribute to the vascular hyporeactivity of BS/GS.

Chronic renal failure, end-stage renal disease, and peritoneal dialysis in Gitelman's syndrome.

The chronic state of hypovolemia, hypotension, and hypokalemia found in Bartter's syndrome has been shown to lead to a chronic nephropathy, which then can progress toward end-stage renal disease and dialysis. This progression, however, has never been reported for Gitelman's syndrome, a variant of Bartter's syndrome that shows a milder clinical picture. This report is the first to document this progression (ie, the development of end-stage renal disease in Gitelman's syndrome) as well as the first report of the use of peritoneal dialysis in either Bartter's syndrome or Gitelman's syndrome. The clinical course highlights the importance of and the need for careful control of hemodynamic status in these patients to slow the progression of renal injury. The hemodynamic alterations that characterize Bartter's syndrome and Gitelman's syndrome patients suggest that for patients requiring renal replacement therapy, peritoneal dialysis is a more appropriate treatment because of its less severe impact on these parameters.

Analysis of Gq protein alpha subunit mRNA expression in human monocytes: relevance of the purification step.

BACKGROUND: Galphaq is a member of the Gq family of G proteins, which by stimulating the phospholipase Cbeta (PLCbeta)-IP(3)-Ca(++) mediated intracellular signaling systems controls some of the most fundamental cardiovascular cellular processes. The study of Galphaq is complicated by the presence of a pseudogene in human DNA, with signficant homology to the mRNA encoding the alpha subunit of Gq protein. The presence of this pseudogene will cause problems when the analysis of the Galphaq gene expression is based solely on RT-PCR. In this study, we report a simple method for avoiding unwanted amplification of the Galphaq pseudogene and the use of human monocytes as a readily available source for examining Galphaq. METHODS: RT-PCR was carried out on RNA extracted from peripheral blood monocytes of 10 normal subjects using specific primers for Galphaq. RESULTS: When several subjects' Galphaq was examined, the authentic Galphaq mRNA amplification product levels, as a ratio to unpurified pseudogene containing amplification products, declined by up to approximately 70%. CONCLUSION: Given the importance of Gq protein in cardiovascular signal transduction, it is fundamental to provide a reliable assessment of G alpha q gene expression. In addition to accurately assessing Galphaq levels, the use of circulating human monocytes as a useful source of Galphaq for investigating mechanisms involved in the regulation of vascular tone is shown.

Effect of insulin and angiotensin II on cell calcium in human skin fibroblasts.

We have recently shown that insulin attenuates angiotensin II-induced intracellular Ca(2+) mobilization in human skin fibroblasts from normotensive subjects. This study was designed to investigate the effects of angiotensin II and the interactions between insulin and angiotensin II on intracellular Ca(2+) mobilization in skin fibroblasts from patients with essential hypertension. Fibroblasts were obtained from 9 normotensives and 18 hypertensives. Spectrofluorophotometric free Ca(2+) measurement was performed in monolayers of 24-hour serum-deprived cells. Resting intracellular Ca(2+) level and angiotensin II-stimulated intracellular Ca(2+) peak were higher in fibroblasts from hypertensives compared with those from normotensives. The effect of acute insulin exposure was evaluated in fibroblasts from hypertensives subdivided on the basis of insulin sensitivity. In insulin-sensitive hypertensives, insulin significantly blunted the effects of angiotensin II on intracellular Ca(2+) response, whereas in insulin-resistant patients, insulin did not modify intracellular Ca(2+) response to angiotensin II. Pertussis toxin, a G(ialpha)-inhibitor, reduced angiotensin II-stimulated Ca(2+) peak in insulin-sensitive but not in insulin-resistant hypertensives. In conclusion, the effects of angiotensin II on intracellular Ca(2+) mobilization are more pronounced in fibroblasts from hypertensives compared with those from normotensives, and the inhibitory effect of insulin is blunted in insulin-resistant hypertensives by a G(ialpha) pertussis toxin-sensitive abnormality.

Adrenomedullin stimulates DNA synthesis of rat adrenal zona glomerulosa cells through activation of the mitogen-activated protein kinase-dependent cascade.

BACKGROUND: Adrenal zona glomerulosa cells are provided with adrenomedullin receptors. Adrenomedullin has recently been found to enhance proliferation of cultured rat vascular smooth muscle cells and zona glomerulosa cells. OBJECTIVE: To investigate whether adrenomedullin affects rat zona glomerulosa proliferative activity through the tyrosine kinase and extracellular signal regulated kinases (ERKs) pathways. METHODS: Dispersed rat zona glomerulosa cells were cultured in vitro for 24 h and then exposed to adrenomedullin (10(-7) mol/l), alone or in the presence of tyrphostin-23 (10(-5) mol/l) or PD-98059 (10(-4) mol/l), for 24 or 48 h. To assess the rate of DNA synthesis, 5-bromo-2'-deoxyuridine (BrdU, 20 mg/ml) was also added to the medium and BrdU-positive cells were detected by immunocytochemistry. The expression of ERKs and the effect of adrenomedullin on ERKs phosphorylation and activity were assayed in dispersed zona glomerulosa cells. RESULTS: Adrenomedullin significantly increased the percentage of BrdU-positive (phase-S) zona glomerulosa cells; this effect was blocked by either the tyrosine kinase inhibitor, tyrphostin-23, or the mitogen-activated protein kinase kinase (MEK-1) inhibitor, PD-98059. Both zona glomerulosa and zona fasciculata/reticularis express ERK-1 (44 kDa) and ERK-2 (42 kDa) isoforms. However, adrenomedullin phosphorylated ERK-1 and ERK-2 only in the zona glomerulosa; this effect was blunted by the MEK-1 inhibitor, PD98059, and by the calcitonin gene-related peptide type 1 (CGRP-1) receptor antagonist, CGRP8-37, but not by the adrenomedullin C-terminal fragment, ADM22-52. CONCLUSION: Adrenomedullin stimulates the growth of rat zona glomerulosa cells through activation of CGRP-1 receptor, linked to the tyrosine kinase-MEK-1-ERKs signalling pathway. These results confirm the complex role played by this peptide in the regulation of zona glomerulosa cell physiology.