Administration Of Deoxycorticosterone Acetate Research Articles

Inhibition of Eicosanoid Degradation Mitigates Fibrosis of the Heart.

Organ fibrosis due to excessive production of extracellular matrix by resident fibroblasts is estimated to contribute to >45% of deaths in the Western world, including those due to cardiovascular diseases such as heart failure. Here, we screened for small molecule inhibitors with a common ability to suppress activation of fibroblasts across organ systems. High-content imaging of cultured cardiac, pulmonary, and renal fibroblasts was used to identify nontoxic compounds that blocked induction of markers of activation in response to the profibrotic stimulus, transforming growth factor-β1. SW033291, which inhibits the eicosanoid-degrading enzyme, 15-hydroxyprostaglandin dehydrogenase, was chosen for follow-up studies with cultured adult rat ventricular fibroblasts and human cardiac fibroblasts (CF), and for evaluation in mouse models of cardiac fibrosis and diastolic dysfunction. Additional mechanistic studies were performed with CFs treated with exogenous eicosanoids. Nine compounds, including SW033291, shared a common ability to suppress transforming growth factor-β1-mediated activation of cardiac, pulmonary, and renal fibroblasts. SW033291 dose-dependently inhibited transforming growth factor-β1-induced expression of activation markers (eg, α-smooth muscle actin and periostin) in adult rat ventricular fibroblasts and normal human CFs, and reduced contractile capacity of the cells. Remarkably, the 15-hydroxyprostaglandin dehydrogenase inhibitor also reversed constitutive activation of fibroblasts obtained from explanted hearts from patients with heart failure. SW033291 blocked cardiac fibrosis induced by angiotensin II infusion and ameliorated diastolic dysfunction in an alternative model of systemic hypertension driven by combined uninephrectomy and deoxycorticosterone acetate administration. Mechanistically, SW033291-mediated stimulation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase signaling was required for the compound to block CF activation. Of the 12 exogenous eicosanoids that were tested, only 12(S)-hydroxyeicosatetraenoic acid, which signals through the G protein-coupled receptor, GPR31, recapitulated the suppressive effects of SW033291 on CF activation. Inhibition of degradation of eicosanoids, arachidonic acid-derived fatty acids that signal through G protein-coupled receptors, is a potential therapeutic strategy for suppression of pathological organ fibrosis. In the heart, we propose that 15-hydroxyprostaglandin dehydrogenase inhibition triggers CF-derived autocrine/paracrine signaling by eicosanoids, including 12(S)-hydroxyeicosatetraenoic acid, to stimulate extracellular signal-regulated kinase 1/2 and block conversion of fibroblasts into activated cells that secrete excessive amounts of extracellular matrix and contribute to heart failure pathogenesis.

Further evidence against the role renal medullary perfusion in short-term control of arterial pressure in normotensive and mildly or overtly hypertensive rats

Earlier evidence from studies of rat hypertension models undermines the widespread view that the rate of renal medullary blood flow (MBF) is critical in control of arterial pressure (MAP). Here, we examined the role of MBF in rats that were normotensive, with modest short-lasting pressure elevation, or with overt established hypertension. The groups studied were anaesthetised Sprague-Dawley rats: (1) normotensive, (2) with acute i.v. norepinephrine-induced MAP elevation, and (3) with hypertension induced by unilateral nephrectomy followed by administration of deoxycorticosterone-acetate (DOCA) and 1% NaCl drinking fluid for 3 weeks. MBF was measured (laser-Doppler probe) and selectively increased using 4-h renal medullary infusion of bradykinin. MAP, renal excretion parameters and post-experiment medullary tissue osmolality and sodium concentration were determined. In the three experimental groups, baseline MAP was 117, 151 and 171 mmHg, respectively. Intramedullary bradykinin increased MBF by 45%, 65% and 70%, respectively, but this was not associated with a change in MAP. In normotensive rats a significant decrease in medullary tissue sodium was seen. The intramedullary bradykinin specifically increased renal excretion of water, sodium and total solutes in norepinephrine-treated rats but not in the two other groups. As previously shown in models of rat hypertension, in the normotensive rats and those with acute mild pressure elevation (resembling labile borderline human hypertension), 4-h renal medullary hyperperfusion failed to decrease MAP. Nor did it decrease in DOCA-salt model mimicking low-renin human hypertension. Evidently, within the 4-h observation, medullary perfusion was not a critical determinant of MAP in normotensive and hypertensive rats.

Daidzein- A Caveolin Inhibitor Exerts Antihypertensive Effect and Improves Endothelium-Dependent Vasorelaxation in a Rat Model of DOCA-Salt-Induced Hypertension

Daidzein- A caveolin inhibitor has antioxidant properties that could improve redox-sensitive vascular, cardiac and renal changes associated with deoxycorticosterone acetate/1% NaCl high salt (DOCA/HS)-induced hypertension. We investigated the possible involvement of caveolin and daidzein its inhibitor in hypertension and endothelial dysfunction in a mineralocorticoid-salt mouse model (DOCA-Salt). Hypertension was induced in sham control mice by nephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment for 6-weeks. (Control uninephrectomized mice drank 1% NaCl water). Nephrectomy + DOCA (40mg/kg, s.c: 6 weeks) administration increased mean arterial blood pressure in rats after 6 weeks as compared to normal control group. VED was assessed in terms of decreased serum nitrite/nitrate conc., reduced glutathione levels, ACh-induced endothelium-dependent vasorelaxation, and SNP-induced endothelium-independent Vasorelaxation. These rats received cotreatment of different doses of daidzein (0.2, 0.4mg/kg/day, sac) for 5 weeks. Daidzein (0.2mg/kg/day., and 0.4 mg/kg/day., sac for 1 week) and lisinopril 1mg/kg., p.o., 1 week) treatment for one week significantly ameliorated VED in hypertensive rats measured in terms of decreased reduced glutathione level, serum nitrite/nitrate conc. increased Ach-induced endothelium-dependent vasorelaxation as compared to the hypertensive group. However, sodium nitroprusside did not produce any change in SNP-induced endothelium-independent vasorelaxation that shows that effect is specifically due to the improvement of endothelium dysfunction. Our results demonstrate that daidzein reduces oxidative stress, prevents development and progression of hypertension as well as cardiac and renal hypertrophy in DOCA/HS-induced hypertension via modulation of activated eNOS, endogenous antioxidants, serum NO.

Transiently proliferating perivascular microglia harbor M1 type and precede cerebrovascular changes in a chronic hypertension model

BackgroundMicroglia play crucial roles in the maintenance of brain homeostasis. Activated microglia show a biphasic influence, promoting beneficial repair and causing harmful damage via M2 and M1 microglia, respectively. It is well-known that microglia are initially activated to the M2 state and subsequently switch to the M1 state, called M2-to-M1 class switching in acute ischemic models. However, the activation process of microglia in chronic and sporadic hypertension remains poorly understood. We aimed to clarify the process using a chronic hypertension model, the deoxycorticosterone acetate (DOCA)-salt-treated Wistar rats.MethodsAfter unilateral nephrectomy, the rats were randomly divided into DOCA-salt, placebo, and control groups. DOCA-salt rats received a weekly subcutaneous injection of DOCA (40 mg/kg) and were continuously provided with 1% NaCl in drinking water. Placebo rats received a weekly subcutaneous injection of vehicle and were provided with tap water. Control rats received no administration of DOCA or NaCl. To investigate the temporal expression profiles of M1- and M2-specific markers for microglia, the animals were subjected to the immunohistochemical and biochemical studies after 2, 3, or 4 weeks DOCA-salt treatment.ResultsHypertension occurred after 2 weeks of DOCA and salt administration, when round-shaped microglia with slightly shortened processes were observed juxtaposed to the vessels, although the histopathological findings were normal. After 3 weeks of DOCA and salt administration, M1-state perivascular and parenchyma microglia significantly increased, when local histopathological findings began to be observed but cerebrovascular destruction did not occur. On the other hand, M2-state microglia were never observed around the vessels at this period. Interestingly, prior to M1 activation, about 55% of perivascular microglia transiently expressed Ki-67, one of the cell proliferation markers.ConclusionsWe concluded that the resting perivascular microglia directly switched to the pro-inflammatory M1 state via a transient proliferative state in DOCA-salt rats. Our results suggest that the activation machinery of microglia in chronic hypertension differs from acute ischemic models. Proliferative microglia are possible initial key players in the development of hypertension-induced cerebral vessel damage. Fine-tuning of microglia proliferation and activation could constitute an innovative therapeutic strategy to prevent its development.

Deoxycorticosterone acetate-salt hypertension activates placental growth factor in the spleen to couple sympathetic drive and immune system activation.

Chronic increase of mineralocorticoids obtained by administration of deoxycorticosterone acetate (DOCA) results in salt-dependent hypertension in animals. Despite the lack of a generalized sympathoexcitation, DOCA-salt hypertension has been also associated to overdrive of peripheral nervous system in organs typically targeted by blood pressure (BP), as kidneys and vasculature. Aim of this study was to explore whether DOCA-salt recruits immune system by overactivating sympathetic nervous system in lymphoid organs and whether this is relevant for hypertension. To evaluate the role of the neurosplenic sympathetic drive in DOCA-salt hypertension, we challenged splenectomized mice or mice with left coeliac ganglionectomy with DOCA-salt, observing that they were both unable to increase BP. Then, we evaluated by immunofluorescence and ELISA levels of the placental growth factor (PlGF) upon DOCA-salt challenge, which significantly increased the growth factor expression, but only in the presence of an intact neurosplenic sympathetic drive. When PlGF KO mice were subjected to DOCA-salt, they were significantly protected from the increased BP observed in WT mice under same experimental conditions. In addition, absence of PlGF hampered DOCA-salt mediated T cells co-stimulation and their consequent deployment towards kidneys where they infiltrated tissue and provoked end-organ damage. Overall, our study demonstrates that DOCA-salt requires an intact sympathetic drive to the spleen for priming of immunity and consequent BP increase. The coupling of nervous system and immune cells activation in the splenic marginal zone is established through a sympathetic-mediated PlGF release, suggesting that this pathway could be a valid therapeutic target for hypertension.

Physalis minima Leaves Extract Induces Re-Endothelialization in Deoxycorticosterone Acetate-Salt-Induced Endothelial Dysfunction in Rats

The administration of deoxy-corticosterone acetate (DOCA)-salt can induce oxidative stress leading to decrease the bioavailability of nitric oxide (NO), increase senescence of circulating endothelial progenitor cells (EPCs), thus contributing to endothelial dysfunction. This study was aimed to investigate the effects of Physalis minima L. leaves extract on serum NO levels, circulating EPCs number, and histopathology of tail artery endothelial cells in DOCA-salt-induced endothelial dysfunction in rats. Twenty-five male Wistar rats were randomly divided into five groups: rats without any treatment (normal), rats treated with DOCA (10 mg/kgBW s.c. twice weekly) and given 0.9% NaCl to drink ad libitum for 6 weeks, and DOCA-salt-induced rats orally supplemented with P. minima leaves extract at doses of 500, 1500, or 2500 mg/kgBW for 4 weeks. Serum NO levels were measured by colorimetry. The number of circulating EPCs (CD34+/CD133+ cells) was determined by flow cytometry. The tail artery sections were histologically processed with hematoxylin-eosin staining. DOCA-salt-induced rats showed significantly (p<0.05) decrease in serum NO levels and circulating EPCs number compared to the normal. There was also more detached tail artery endothelial cells in DOCA-salt-induced rats. P. minima leaves extract at a dose of 500 mg/kgBW significantly (p<0.05) increased serum NO level and circulating EPCs number, and also induced an optimal re-endothelialization in DOCA-salt-induced rats. P. minima leave extract dose-dependently increases NO bioavailability contributing to enhanced EPCs mobilization, thereby promoting re-endothelialization in DOCA-salt-induced endothelial dysfunction in rats.

A New Mouse Model for Introduction of Aortic Aneurysm by Implantation of Deoxycorticosterone Acetate Pellets or Aldosterone Infusion in the Presence of High Salt.

Dysfunction of the renin-angiotensin-aldosterone system (RAAS) has been implicated in the etiologies of many cardiovascular diseases, including aortic aneurysm. In particular, the infusion of angiotensin II (Ang II) in the apolipoprotein E-deficient mice (apoE-/-) and low density lipoprotein receptor knockout mice (LDLR-/-) to induce aortic aneurysm has been extensively used in the field. In contrast, whether aldosterone (Aldo), an essential component of RAAS and a downstream effector of Ang II, is involved in aortic aneurysm is largely unknown. Here, we describe a new animal model for induction of aortic aneurysm in mice in which administration of deoxycorticosterone acetate (DOCA) and high salt or aldosterone and high salt, but not DOCA or high salt alone, to C57BL/6 male mice can potently induce aortic aneurysm formation and rupture in an age-dependent manner. This new aortic aneurysm mouse model is different from Ang II infusion mouse model and exhibits several unique features that mimic human aortic aneurysm.

CS-3150, a Novel Nonsteroidal Mineralocorticoid Receptor Antagonist, Shows Preventive and Therapeutic Effects On Renal Injury in Deoxycorticosterone Acetate/Salt-Induced Hypertensive Rats.

The present study was designed to assess both preventive and therapeutic effects of (S)-1-(2-Hydroxyethyl)-4-methyl-N-[4-(methylsulfonyl) phenyl]-5-[2-(trifluoromethyl) phenyl]-1H-pyrrole-3-carboxamide (CS-3150), a novel nonsteroidal mineralocorticoid receptor antagonist, on renal injury in deoxycorticosterone acetate (DOCA)/salt-induced hypertensive rats (DOCA rats). From 7 weeks of age, DOCA was subcutaneously administered once a week for 4 weeks to uninephrectomized rats fed a high-salt diet. In experiment 1, CS-3150 (0.3-3 mg/kg) was orally administered once a day for 4 weeks coincident with DOCA administration. In experiment 2, after establishment of renal injury by 4 weeks of DOCA/salt loading, CS-3150 (3 mg/kg) was orally administered once a day for 4 weeks with or without continuous DOCA administration. In experiment 1, DOCA/salt loading significantly increased systolic blood pressure (SBP), which was prevented by CS-3150 in a dose-dependent manner. Development of renal injury (proteinuria, renal hypertrophy, and histopathological changes in glomeruli and tubule) was also suppressed by CS-3150 with inhibition of mRNA expression of fibrosis, inflammation, and oxidative stress markers. In experiment 2, under continuous DOCA treatment, CS-3150 clearly ameliorated existing renal injury without lowering SBP, indicating that CS-3150 regressed renal injury independent of its antihypertensive action. Moreover, CS-3150 treatment in combination with withdrawal of DOCA showed further therapeutic effect on renal injury accompanied by reduction in SBP. These results demonstrate that CS-3150 not only prevents but also ameliorates hypertension and renal injury in DOCA rats. Therefore, CS-3150 could be a promising agent for the treatment of hypertension and renal disorders, and may have potential to promote regression of renal injury.

Activation of Brain Angiotensin Type‐2 Receptors Reverses DOCA‐salt Hypertension in Mice

These studies assess the impact of activating brain angiotensin type‐2 receptors (AT2R) on blood pressure in a mouse model of hypertension. Experiments combine the use of a transgenic AT2R green fluorescent protein reporter mouse with in situ hybridization (ISH) to reveal that AT2R‐containing cells are localized to brain regions that regulate cardiovascular function. In particular, the nucleus of the solitary tract (NTS) densely expresses AT2R, primarily in glutamic acid decarboxylase‐1 (Gad1)‐containing (i.e., GABAergic) neurons. Based on this localization and the known hypertensive actions of GABA in the NTS, we hypothesized that brain AT2R activation would reverse hypertension in mice via the inhibition of NTS GABA signaling. Mice were initially rendered hypertensive via administration of deoxycorticosterone acetate and consumption of isotonic saline (DOCA‐salt) or served as normotensive controls. Subsequently, the impact of the chronic administration of the selective AT2R agonist, compound 21 (C21; 7.5 ng/h into the lateral cerebral ventricle [icv]) on blood pressure and gene expression within the NTS were assessed. Chronic icv C21 reduced baseline blood pressure relative to control mice and reversed DOCA‐salt hypertension. Gene expression studies revealed that DOCA‐salt hypertension was associated with elevated Gad1 and AT2R mRNAs within the NTS. The antihypertensive actions of C21 were associated with decreased Gad1 mRNA in the NTS, suggestive of reduced GABAergic signaling. Collectively, the present results indicate that AT2R activation using C21 reverses DOCA‐salt hypertension and that this is accompanied by alterations in NTS gene expression that are consistent with NTS GABAergic signaling playing a role in these effects.

Purinergic receptors in tubulointerstitial inflammatory cells: a pathophysiological mechanism of salt-sensitive hypertension.

Recent studies have suggested that both the tubulointerstitial inflammatory cells and the activation of purinergic receptors integrate common mechanisms that result in salt-sensitive hypertension. The basis of this hypothesis is that renal endothelial cells release ATP in response to shear stress in the setting of hypertension. It has been demonstrated that the over-expression and activation of the P2X7, P2Y12 and P2X1 receptors favour the elevation of blood pressure induced by high-salt intake. In addition, the release of interleukins and inflammatory mediators in the tubulointerstitial area appears to be related to the activation of these receptors. Renal vasoconstriction and tubulointerstitial injury develop as a result, which increase sodium reabsorption by epithelial cells. Consistent with these effects, the reduction of tubulointerstitial inflammation caused by immunosuppressants, such as mycophenolate mofetil, prevents the development of salt-sensitive hypertension. Also, P2X7-receptor knockout mice develop minor renal injury when hypertension is induced via the administration of deoxycorticosterone acetate and a high-salt diet. In the setting of angiotensin II-induced hypertension, which is an early stage in the development of salt-sensitive hypertension, an acute blockade with the specific, non-selective P2 antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid prevented the renal vasoconstriction induced by angiotensin II. In addition, it normalized glomerular haemodynamics and restored sodium excretion to control values. These findings suggest that chronic administration of P2 purinergic antagonists may prevent the deleterious effects of purinergic receptors during the development of salt-sensitive hypertension.

Consumption of a high n-3 polyunsaturated fatty acid diet during gradual mild physiological stress in rats

n-3 Polyunsaturated fatty acids (n-3PUFAs) may be beneficial for anxiety and depression under stressful conditions. Studies however, typically utilise physical or sudden physiological stress, while gradual physiological stress is also relevant to human conditions. Using deoxycorticosterone acetate (DOCA) administration to induce gradual physiological stress, this study investigated the impact of n-3PUFAs under gradual physiological stress in rats. Animals (aged 2 months) (N=8–12/group) received daily injections of DOCA or vehicle and were concurrently fed a high n-3PUFA or control diet for eight weeks. Behavioural measures were taken throughout. Behavioural tests and physiological measures were conducted after six and eight weeks respectively. DOCA administration decreased plasma renin, plasma proteins and relative adrenal weight, and increased water intake, relative kidney weight, and anxiety in the open field. These findings demonstrate disruptions to the renin–angiotensin–aldosterone system, a result of mild physiological stress, that also impact on anxiety behaviours. No effects of n-3PUFAs were found.

Evaluation of the antihypertensive activity and alpha adrenergic receptor interaction of cleistanthins A and B.

Hypertension was induced in male Sprague Dawley rats with twice weekly administration of deoxycorticosterone acetate (DOCA) salt (20 mg/kg s.c) for 4 weeks. They were divided into eight groups of six animals each viz., hypertensive control, standard (prazosin 1 mg/kg), cleistanthin A 12.5, 25, 50 mg/kg and cleistanthin B 12.5, 25 mg/kg, and 50 mg/kg. One more group served as normal control. The hypertension was induced in 4 weeks, and the animals were given assigned treatment in 5th week. The alteration in blood pressure (BP) was recorded weekly using a rodent noninvasive blood pressure system. At the end of the experiment alpha-adrenergic receptor response of drugs like adrenaline, nor adrenaline, dopamine (doses 1 μg and 2 μg) was recorded invasively. Two-way repeated measures ANOVA followed by Bonferroni post-hoc test was used to analyze the data. The systolic BP and diastolic BP of test groups rose to a higher level after DOCA administration and fell to the normal range (P < 0.05) following the administration of cleistanthins A and B. There were no differences in the weekly heart rate among the groups. In the test group animals pretreated with prazosin and cleistanthins, adrenaline, noradrenaline and dopamine failed to raise the mean arterial pressure and the end-diastolic pressure from baseline (P > 0.05) cleistanthins A and B exert a significant antihypertensive effect through alpha-adrenergic receptor blockade similar to prazosin.

Abstract 447: Intracerebroventricular Administration of Autologous Bone Marrow-derived Cells Attenuates Sympathetic Hyperactivity in Deoxycorticosterone Acetate-salt Hypertensive Rats

Objectives: Administration of deoxycorticosterone acetate (DOCA) in combination with salt loading and surgical removal of one kidney induces hypertension. Central mechanism is involved in this hypertension. Bone marrow-derived cells (BMCs) include mesenchymal stem cells play critical role in repairing damaged tissue and anti-inflammation. We hypothesized that increase in number of BMCs in the brain would attenuate the DOCA-salt hypertension. Methods: Sprague-Dawley rats underwent unilateral nephrectomy were divided into following 4 groups: rats received sham treatment with intracerebroventricular (icv) administration of medium (S/M group, n=5); rats received sham treatment with icv administration of BMCs (S/B group, n=5); rats received DOCA-salt treatment with icv administration of medium (D/M group, n=4); rats received DOCA-salt treatment with icv administration of BMCs (D/B group, n=7). Three weeks following the initiation of DOCA-salt treatment, rats had surgery to implant arterial and venous catheters. Resting mean arterial pressure (MAP) of rats was recorded in conscious unrestrained state and resting sympathetic tone was evaluated with a peak depressor response produced by hexamethonium (C6) injection. Results: Resting MAPs of S/M, S/B, D/M and D/B group were 116±4, 120±5, 194±4, 172±9 mmHg, respectively. DOCA-salt treatment significantly increased MAP in both D/M and D/B group. D/B group tended to have lower MAP than D/M group, however, post hoc analysis did not reach significant. The peak depressor responses to C6 injection in S/M, S/B, D/M and D/B group were 41±2, 46±5, 97±10, 69±5 mmHg, respectively. DOCA-salt treatment significantly increased the peak depressor response to C6 and icv administration of BMCs attenuated the increase in peak depressor response. Conclusion: BMCs in the brain may have protective role against sympathetic hyperactivity caused by DOCA-salt treatment.

Mineralocorticoid receptor agonists induce mouse aortic aneurysm formation and rupture in the presence of high salt.

Elevated plasma aldosterone concentrations in patients have been linked to a spectrum of cardiovascular diseases. Mineralocorticoid receptor antagonists provide additional benefits in patients with heart failure. However, whether aldosterone and the mineralocorticoid receptor are involved in aortic aneurysm is unknown. We report that administration of deoxycorticosterone acetate (DOCA) and salt or aldosterone and salt, but not DOCA or salt alone, to C57BL/6 male mice induced abdominal and thoracic aortic aneurysm formation and rupture in an age-dependent manner. DOCA and salt- or aldosterone and salt-induced aortic aneurysm mimicked human aortic aneurysm with respect to elastin degradation, inflammatory cell infiltration, smooth muscle cell degeneration and apoptosis, and oxidative stress. Aortic aneurysm formation did not correlate with the increase in blood pressure induced by DOCA and salt. Systemic administration of the angiotensin-converting enzyme inhibitor, enalapril, or angiotensin type 1 receptor antagonist, losartan, did not affect DOCA and salt-induced aortic aneurysm. In contrast, the mineralocorticoid receptor antagonists, spironolactone or eplerenone, significantly attenuated DOCA and salt- or aldosterone and salt-induced aortic aneurysm. The current study describes a novel aortic aneurysm animal model induced by mineralocorticoid receptor agonist and high salt, and reveals a previously unrecognized but potentially significant role of aldosterone in the pathogenesis of aortic aneurysm. These findings imply that mineralocorticoid receptor antagonists may be effective in the treatment of some aortic aneurysms.

Effect of combination of renin inhibitor and Mas-receptor agonist in DOCA–salt-induced hypertension in rats

To investigate the combined effect of aliskiren, a renin inhibitor, and AVE 0991, a Mas-receptor agonist, in experimental hypertension (HT) in rats. HT was produced by administration of deoxycorticosterone acetate (DOCA) and mean arterial blood pressure (MABP) was assessed by tail-cuff method. Treatments were started from 4th week onwards and were continued for 9 days. A significant increase in MABP was noted after 1 week in DOCA control rats, as compared with the base line value. A stable HT developed after 4 weeks of DOCA administration. Treatments with aliskiren and AVE 0991 alone, dose-dependently decreased MABP in DOCA-treated rats. Further, combination of low doses of aliskiren and AVE 0991 significantly reduced MABP, as compared with DOCA control rats and with either drug alone in low doses. It may be concluded that treatment with aliskiren produced down-regulation of both harmful Ang II-AT1-receptor and survival Ang(1-7)/Mas-receptor axis of RAAS. Treatment with combination of low doses of aliskiren and AVE 0991, for the first time, has been shown to produce synergistic blood pressure lowering effect. Therefore, combination of renin inhibitor with Mas-receptor agonist may prove beneficial for the treatment of hypertensive patients.

Whole brain tyrosine hydroxylase activity during the development of deoxycorticosterone acetate-1% sodium chloride-induced hypertension in rats.

Water was chosen as the optimal medium for the extraction of tyrosine hydroxylase (TH) from rat brain. Determination of TH activity in crude homogenates failed to exhibit a linear relationship between enzyme concentration and measured activity, however, when a supernatant was used, a linear relationship existed. At a time when TH activity is maximally increased in the locus coeruleus after reserpine treatment (Reis et al 1975; Zigmond.1979) (2.5 mg kg-1 day-1 for 3 days, kill 24 h after last dose) we could detect no alterations in whole brain TH, however if treatment continued for 4 days and animals were killed 72 h after the last dose it was possible to detect increases in TH activity in various brain regions. These results suggest that local changes in brain TH activity are not revealed in measurements made on whole brain. The early rise in blood pressure, following the administration of deoxycorticosterone acetate (doca) and 1% NaCl to male Wistar rats, was accompanied by bradycardia. Whole brain Th activity was determined in these hypertensive animals 6-21 days after the commencement of treatment and the results failed to confirm the reported elevation of TH activity (Rylett et al 1976). The results are discussed with reference to the TH assay employed.

Development of DOCA-salt Hypertension in Guinea-pigs: Effects of Indapamide

The effects of indapamide on the development of cardiac complications related to deoxycorticosterone acetate (DOCA)-salt-induced hypertension in guinea-pigs have been studied. Indapamide treatment (5 mg kg−1 daily) was initiated either before DOCA administration or five weeks after DOCA administration, for a period of five weeks. Increase in blood pressure was prevented or attenuated by indapamide (−19%, P<0·05). In parallel, development of cardiac hypertrophy assessed by an increase in left ventricular weight, thickness and volume was also prevented (−13, −25 and −25%, respectively, all P<0·05) or attenuated (-7·5, −15%, P<0·05 and −9·8%, respectively). DOCA-salt treatment over a longer period (10 weeks) led rapidly to the appearance of signs of heart failure with pleural or pericardial effusion. Indapamide-treated guinea-pigs presented no such signs of heart failure. These results demonstrate that the DOCA-salt guinea-pig is a suitable model for studying hypertensive disease. Indapamide prevents and produces a regression in hypertension and cardiac hypertrophy, and prevents the development of heart failure.

Mild DOCA-salt hypertension: sympathetic system and role of renal nerves

Excess sympathetic nervous system activity (SNA) is linked to human essential and experimental hypertension. To test whether sympathetic activation is associated with a model of deoxycorticosterone acetate (DOCA)-salt hypertension featuring two kidneys and a moderate elevation of blood pressure, we measured whole body norepinephrine (NE) spillover as an index of global SNA. Studies were conducted in chronically catheterized male Sprague-Dawley rats drinking water containing 1% NaCl and 0.2% KCl. After a 7-day surgical recovery and a 3-day control period, a DOCA pellet (50 mg/kg) was implanted subcutaneously in one group of rats (DOCA), while the other group underwent sham implantation (Sham). NE spillover was measured on control day 2 and days 7 and 14 after DOCA administration or sham implantation. During the control period, mean arterial pressure (MAP) was similar in Sham and DOCA rats. MAP was significantly increased in the DOCA group compared with the Sham group after DOCA administration (day 14: Sham = 109 ± 5.3, DOCA = 128 ± 3.6 mmHg). However, plasma NE concentration, clearance, and spillover were not different in the two groups at any time. To determine whether selective sympathetic activation to the kidneys contributes to hypertension development, additional studies were performed in renal denervated (RDX) and sham-denervated (Sham-DX) rats. MAP, measured by radiotelemetry, was similar in both groups during the control and DOCA treatment periods. In conclusion, global SNA is not increased during the development of mild DOCA-salt hypertension, and fully intact renal nerves are not essential for hypertension development in this model.

The DOCA-Salt Hypertensive Rat as a Model of Cardiovascular Oxidative and Inflammatory Stress

Oxidative stress and inflammation are two sides of the same coin that are intricately combined to elicit a chronic pathophysiological stress state, especially as seen in cardiovascular remodelling. In this review, we argue that administration of deoxycorticosterone acetate (DOCA) and sodium chloride to uninephrectomised rats, defined as DOCA-salt hypertensive rats, provides a reliable animal model of oxidative and inflammatory stress in the cardiovascular system. The supporting evidence includes pathophysiological and biochemical changes together with pharmacological responses to synthetic and natural compounds that lower the concentrations of reactive free radical species and that curtail inflammatory responses in the cardiovascular system.

Mineralocorticoid Accelerates Transition to Heart Failure With Preserved Ejection Fraction Via “Nongenomic Effects”

Mechanisms promoting the transition from hypertensive heart disease to heart failure with preserved ejection fraction are poorly understood. When inappropriate for salt status, mineralocorticoid (deoxycorticosterone acetate) excess causes hypertrophy, fibrosis, and diastolic dysfunction. Because cardiac mineralocorticoid receptors are protected from mineralocorticoid binding by the absence of 11-beta hydroxysteroid dehydrogenase, salt-mineralocorticoid-induced inflammation is postulated to cause oxidative stress and to mediate cardiac effects. Although previous studies have focused on salt/nephrectomy in accelerating mineralocorticoid-induced cardiac effects, we hypothesized that hypertensive heart disease is associated with oxidative stress and sensitizes the heart to mineralocorticoid, accelerating hypertrophy, fibrosis, and diastolic dysfunction. Cardiac structure and function, oxidative stress, and mineralocorticoid receptor-dependent gene transcription were measured in sham-operated and transverse aortic constriction (studied 2 weeks later) mice without and with deoxycorticosterone acetate administration, all in the setting of normal-salt diet. Compared with sham mice, sham plus deoxycorticosterone acetate mice had mild hypertrophy without fibrosis or diastolic dysfunction. Transverse aortic constriction mice displayed compensated hypertensive heart disease with hypertrophy, increased oxidative stress (osteopontin and NOX4 gene expression), and normal systolic function, filling pressures, and diastolic stiffness. Compared with transverse aortic constriction mice, transverse aortic constriction plus deoxycorticosterone acetate mice had similar left ventricular systolic pressure and fractional shortening but more hypertrophy, fibrosis, and diastolic dysfunction with increased lung weights, consistent with heart failure with preserved ejection fraction. There was progressive activation of markers of oxidative stress across the groups but no evidence of classic mineralocorticoid receptor-dependent gene transcription. Pressure-overload hypertrophy sensitizes the heart to mineralocorticoid excess, which promotes the transition to heart failure with preserved ejection fraction independently of classic mineralocorticoid receptor-dependent gene transcription.