NF-kappaB activation is required for the development of cardiac hypertrophy in vivo

In the present study, we examined whether NF-kappaB activation is required for cardiac hypertrophy in vivo. Cardiac hypertrophy in rats was induced by aortic banding for 1, 3, and 5 days and 1-6 wk, and age-matched sham-operated rats served as controls. In a separate group of rats, an IkappaB-alpha dominant negative mutant (IkappaB-alphaM), a superrepressor of NF-kappaB activation, or pyrrolidinedithiocarbamate (PDTC), an antioxidant that can inhibit NF-kappaB activation, was administered to aortic-banded rats for 3 wk. The heart weight-to-body weight ratio was significantly increased at 5 days after aortic banding, peaked at 4 wk, and remained elevated at 6 wk compared with age-matched sham controls. Atrial natriuretic peptide and brain natriuretic peptide mRNA expressions were significantly increased after 1 wk of aortic banding, reached a maximum between 2 and 3 wk, and remained increased at 6 wk compared with age-matched sham controls. NF-kappaB activity was significantly increased at 1 day, reached a peak at 3 wk, and remained elevated at 6 wk, and IKK-beta activity was significantly increased at 1 day, peaked at 5 days, and then decreased but remained elevated at 6 wk after aortic banding compared with age-matched sham controls. Inhibiting NF-kappaB activation in vivo by cardiac transfection of IkappaB-alphaM or by PDTC treatment significantly attenuated the development of cardiac hypertrophy in vivo with a concomitant decrease in NF-kappaB activity. Our results suggest that NF-kappaB activation is required for the development of cardiac hypertrophy in vivo and that NF-kappaB could be an important target for inhibiting the development of cardiac hypertrophy in vivo.     

Prolonged tissue PO2 reduction after contraction in spinotrapezius muscle of spontaneously hypertensive rats

We tested the hypothesis that a deficit in oxygen extraction or an increase in oxygen demand after skeletal muscle contraction leads to delayed recovery of tissue oxygen tension (Po(2)) in the skeletal muscle of hypertensive rats compared with normotensive rats. Blood flow and Po(2) recovery at various sites in the spinotrapezius muscle of spontaneously hypertensive rats (SHRs) were evaluated after a 3-min period of muscle contraction and were compared with corresponding values in Wistar-Kyoto rats (WKYs). The recovery of tissue Po(2) [75 +/- 7 (SHRs) vs. 99 +/- 12% (WKYs) of resting values] and venular Po(2) [72 +/- 13 (SHRs) vs. 104 +/- 10% (WKYs) of resting values] were significantly depressed in the SHRs 30 s postcontraction. The delayed recovery persisted for 120 s postcontraction for both tissue [86 +/- 11 (SHRs) vs. 119 +/- 13% (WKYs) of resting values] and venular [74 +/- 2 (SHRs) vs. 100 +/- 9% (WKYs) of resting values] Po(2) levels. There was no significant difference in the recovery of arteriolar Po(2) between the two groups 30 s postcontraction [95 +/- 7 (SHRs) vs. 84 +/- 8% (WKYs) of resting values]. Values for resting diameter of arcade arterioles in the two groups were not different [52 +/- 3 (SHRs) vs. 51 +/- 3 microm (WKYs)], but the arteriolar diameter after the 3-min contraction period was greater in the SHRs (71 +/- 4 microm) than the WKYs (66 +/- 4). Likewise, red blood cell (RBC) velocity [5.8 +/- 0.3 (SHRs) vs. 4.7 +/- 0.2 mm/s (WKYs)] and blood flow [23.0 +/- 0.8 (SHRs) vs. 16.0 +/- 1.0 nl/s (WKYs)] measurements were significantly greater in the SHRs at 30 s postcontraction. The delayed recovery of tissue Po(2) in the SHRs compared with the WKYs can be explained by a decrease in oxygen diffusion from the rarefied microvascular network due to the increased RBC velocity and the shorter residence time in the microcirculation and the consequent disequilibrium for oxygen between plasma and RBCs. The delayed recovery of venular Po(2) in the SHRs is consistent with this explanation, as venular Po(2) is slowly restored to baseline by release of oxygen from the RBCs. This leaves the arterioles in the primary role as oxygen suppliers to restore Po(2) in the tissue after muscle contraction.     

D(1) dopamine receptor regulation of NHE3 during development in spontaneously hypertensive rats

To determine if the defective interactions among D(1)-like receptors, G proteins, and Na(+)/H(+) exchanger 3 (NHE3) are consequences of hypertension, we studied these interactions in rats, before (2--3 wk) and after (12 wk) the establishment of hypertension. To eliminate the confounding influence of second messenger action on D(1) receptor-NHE3 interaction, studies were performed in renal brush-border membranes (BBM) devoid of cytoplasmic second messengers. NHE3 activity increased with age in Wistar-Kyoto (WKY) rats (3 wk = 1.48 +/- 0.39, n = 13; 12 wk = 2.83 +/- 0.15, n = 16, P < 0.05) but not in spontaneously hypertensive rats (SHRs; 3 wk = 2.52 +/- 0.37, n = 11; 12 wk = 2.81 +/- 0.20, n = 16). D(1) receptor protein tended to decrease, whereas NHE3 protein tended to increase with age in both WKY and SHRs. However, the inhibitory effect of a D(1)-like agonist, SKF-81297, on NHE3 activity increased with age in WKY rats (3 wk = -40.7 +/- 5.3%, n = 10, 12 wk = -58.7 +/- 4.6%, n = 12, P < 0.05) but not in SHRs (3 wk = -27.6 +/- 5.9%, n = 11, 12 wk = -25.1 +/- 3.2%, n = 11). The decreased inhibitory effect of another D(1)-like agonist, fenoldopam, on NHE3 activity in SHRs was not caused by increased activity and binding of G beta gamma to NHE3 as has been reported in young WKY rats. G(s)alpha mediates, in part, the inhibitory effect of D(1)-like agonists on NHE3 activity. In WKY rats, fenoldopam increased G(s)alpha/NHE3 binding to the same extent in 2-wk-old (1.5-fold, n = 4) and adult (1.5-fold, n = 4) rats. In contrast, in SHRs, fenoldopam decreased the amount of G(s)alpha bound to NHE3 in 2-wk-old SHRs and had no effect in 4-wk-old and adult SHRs. These studies indicate that the decreased inhibitory effect of D(1)-like agonists on NHE3 activity in SHRs (compared with WKY rats) precedes the development of hypertension. This may be caused, in part, by a decreased interaction between G(s)alpha and NHE3 in BBM secondary to impaired D(1)-like receptor function.     

ε-Viniferin Is More Effective Than Its Monomer Resveratrol in Improving the Functions of Vascular Endothelial Cells and the Heart

The present study compared the effects of resveratrol and its dimer ε-viniferin on vascular endothelial cells (VECs) functions, and on the blood pressure and cardiac mass of spontaneously hypertensive rats (SHRs). Treatment of VECs with these compounds enhanced cell proliferation via nitric oxide generation and protected the cells from oxidative stress by suppressing increases in intracellular oxygen species. ε-Viniferin was more potent than resveratrol in most of these effects. ε-Viniferin, but not resveratrol inhibited angiotensin-converting enzyme activity in vitro. Three weeks of ε-viniferin treatment (5 mg/kg) reduced the systolic blood pressure and improved the whole cardiac mass and left ventricle mass indexes in SHRs. In contrast, resveratrol administration (2.5 mg/kg) failed to lower the blood pressure and significantly improve these mass indexes. These data suggest that ε-viniferin as well as resveratrol may be involved in protecting the functions of VECs and the heart.     

自发性高血压大鼠心肌肥厚和心肌MAPK、AngⅡ的关系

放免法测定自发性高血压大鼠（ＳＨＲ）血浆及心肌血管紧张素Ⅱ（ＡｎｇⅡ）含量,凝胶内磷酸化法测定心肌丝裂素活化蛋白激酶活性（ＭＡＰＫ）,以心脏重／体重表示心肌肥厚程度。结果表明：与４个月的ＷＫＹ大鼠比较,４个月的ＳＨＲ血浆和心肌组织ＡｎｇⅡ及心肌ＭＡＰＫ活性分别增加了２１８．６％、１０１．２％和１０７．０％,心肌肥大程度严重,其中ＭＡＰＫ活性与心肌肥大程度呈明显正相关。提示４个月ＳＨＲ心肌肥厚可能是     

ε-Viniferin is more effective than its monomer resveratrol in improving the functions of vascular endothelial cells and the heart

The present study compared the effects of resveratrol and its dimer ε-viniferin on vascular endothelial cells (VECs) functions, and on the blood pressure and cardiac mass of spontaneously hypertensive rats (SHRs). Treatment of VECs with these compounds enhanced cell proliferation via nitric oxide generation and protected the cells from oxidative stress by suppressing increases in intracellular oxygen species. ε-Viniferin was more potent than resveratrol in most of these effects. ε-Viniferin, but not resveratrol inhibited angiotensin-converting enzyme activity in vitro. Three weeks of ε-viniferin treatment (5 mg/kg) reduced the systolic blood pressure and improved the whole cardiac mass and left ventricle mass indexes in SHRs. In contrast, resveratrol administration (2.5 mg/kg) failed to lower the blood pressure and significantly improve these mass indexes. These data suggest that ε-viniferin as well as resveratrol may be involved in protecting the functions of VECs and the heart.     

Metalloproteinase inhibition by Batimastat attenuates pulmonary hypertension in chronically hypoxic rats

Chronic hypoxia induces lung vascular remodeling, which results in pulmonary hypertension. We hypothesized that a previously found increase in collagenolytic activity of matrix metalloproteinases during hypoxia promotes pulmonary vascular remodeling and hypertension. To test this hypothesis, we exposed rats to hypoxia (fraction of inspired oxygen = 0.1, 3 wk) and treated them with a metalloproteinase inhibitor, Batimastat (30 mg/kg body wt, daily ip injection). Hypoxia-induced increases in concentration of collagen breakdown products and in collagenolytic activity in pulmonary vessels were inhibited by Batimastat, attesting to the effectiveness of Batimastat administration. Batimastat markedly reduced hypoxic pulmonary hypertension: pulmonary arterial blood pressure was 32 +/- 3 mmHg in hypoxic controls, 24 +/- 1 mmHg in Batimastat-treated hypoxic rats, and 16 +/- 1 mmHg in normoxic controls. Right ventricular hypertrophy and muscularization of peripheral lung vessels were also diminished. Batimastat had no influence on systemic arterial pressure or cardiac output and was without any effect in rats kept in normoxia. We conclude that stimulation of collagenolytic activity in chronic hypoxia is a substantial causative factor in the pathogenesis of pulmonary vascular remodeling and hypertension.     

Decreased sensitivity of aorta from hypertensive rats to vasorelaxation by tyrphostin

The role of protein tyrosine kinases (PTKs) in vascular smooth muscle (VSM) contraction was examined in spontaneously hypertensive rats (SHRs). Aorta from SHRs was hyperresponsive to PTK-mediated contraction relative to normotensive Wistar-Kyoto rats (WKYs). Aorta from SHR was also hyporesponsive to vasorelaxation by tyrphostin, a selective inhibitor of PTKs. Further, we found alterations in PTK activity in aorta from SHRs. PDGF stimulated PTK activity to a greater extent in the SHR. Tyrphostin inhibited PDGF-induced PTK stimulation in both strains, however, activity returned to basal levels in the WKY only. The results suggest that PTKs may be involved in VSM contraction and in the development of hypertension.     

Modification of subcellular organelles in pressure-overloaded heart by etomoxir, a carnitine palmitoyltransferase I inhibitor.

To examine the signals regulating cardiac growth and molecular structure of subcellular organelles, cardiac hypertrophy was induced in rats by constriction of the abdominal aorta for 12-13 wk or by treatment with a carnitine palmitoyltransferase I inhibitor, etomoxir (12-15 mg/kg body wt) for 12-13 wk. In contrast to pressure overload, etomoxir redistributed the myosin isozyme population from V3 to V1 and increased the sarcoplasmic reticulum (SR) Ca(2+)-stimulated ATPase activity. When rats with pressure-overloaded hearts were treated with etomoxir, the cardiac hypertrophy was increased whereas the shift in myosin isozymes from V1 to V3 was prevented and the depression in SR Ca(2+)-stimulated ATPase activity was reversed. Plasma thyroid hormone and insulin concentrations were not altered but triglyceride concentrations were reduced in etomoxir-treated rats with pressure overload. The data demonstrate a dissociation between cardiac muscle growth and changes in subcellular organelles and indicate that a shift in myocardial substrate utilization may represent an important signal for molecular remodeling of the heart.     

Cardiovascular effects of prorenin blockade in genetically spontaneously hypertensive rats on normal and high-salt diet

Recent reports have demonstrated a potential role of tissue prorenin in the pathogenesis of cardiovascular and renal damage. This study was designed to examine the role of prorenin in the pathogenesis of target organ damage in spontaneously hypertensive rats (SHRs), the best naturally occurring experimental model of essential hypertension. To this end, we studied 20-wk-old male SHRs receiving a normal diet and 8-wk-old male SHRs given food with 8% NaCl. One-half the rats in each group were given prorenin inhibitor (PRAM-1, 0.1 mg.kg(-1).day(-1)) via osmotic minipumps; the other half served as controls. Arterial pressure, left ventricular function, cardiovascular mass indexes, cardiac fibrosis, and renal function were examined at the end of the experiment. Arterial pressure was unaffected by PRAM-1 in rats on either regular or salt-excess diets. In those rats receiving a normal diet, the blockade of prorenin activation consistently reduced left ventricular mass but affected no other variable. Salt-loaded rats given PRAM-1 for 8 wk demonstrated (1) reduced serum creatinine level, (2) decreased left ventricular mass, (3) improved left ventricular function, and (4) reduced left ventricular fibrosis. These data demonstrated that the blockade of nonproteolytic activation of prorenin exerted significant cardiovascular and renal benefit in SHRs with cardiovascular damage produced by salt excess and suggested that the activation of cardiovascular or renal prorenin may be a major mechanism that mediates cardiac and renal damage in this form of accelerated hypertension.     

Nifedipine-resistant Ca(++)-induced contraction in tail artery of spontaneously hypertensive rats.

Nifedipine-resistant Ca(++)-induced contractions (NR-Ca(++)-contraction) were compared in the tail arteries from SHRs and WKYs (5 and 13 week old). NR-Ca(++)-contraction of tail artery was defined as follows: Ca(++)-induced contraction in the presence of norepinephrine (NE) (10(-5) M) or 5-hydroxytryptamine (5-HT) (10(-5) M) in Ca(++)-free medium containing EGTA (0.1 mM) and nifedipine (10(-6) M). NR-Ca(++)-contractions in arteries from 5 week old SHRs and WKYs were not different. In contrast, NR-Ca(++)-contractions in arteries from 13 week old SHRs were about 2-fold greater than in arteries from 13 week old WKYs. In arteries from 13 week old WKYs and SHRs, nitroglycerin (10(-5) M) significantly reduced the NR-Ca(++)-contraction in the presence of 5-HT but not in the presence of NE. The reduction was inhibited by the presence of methylene blue (3 x 10(-6) M). 8-Bromo-cGMP (10(-4) M) reduced significantly the NR-Ca(++)-contraction in the presence of 5-HT in arteries from 13 week old SHRs and WKYs. The present experiments clearly demonstrated that the NR-Ca(++)-contractions (both in the presence of NE and 5-HT) in 13 week old SHRs were significantly greater than those in arteries from 13 week old WKYs. These results suggest that in addition to an increase in voltage-operated Ca++ mobilization reported by others, an increase in NR-Ca++ mobilization may contribute to the development of hypertension in SHR.     

Nuclear factor-kappaB inhibition by pyrrolidinedithiocarbamate attenuates gastric ischemia-reperfusion injury in rats

Pyrrolidinedithiocarbamate (PDTC) is a potent antioxidant and an inhibitor of nuclear factor-kappaB (NF-kappaB). The present study examined the impact of PDTC preconditioning on gastric protection in response to ischemia-reperfusion (I/R) injury to the rat stomach. Male Wistar rats were recruited and divided into 3 groups (n = 7). One group was subjected to gastric ischemia for 30 min and reperfusion for 1 hour. The second group of rats was preconditioned with PDTC (200 mg/kg body mass i.v.) 15 min prior to ischemia and before reperfusion. The third group of rats was sham-operated and served as the control group. Gastric I/R injury increased serum lactate dehydrogenase level, vascular permeability of gastric mucosa (as indicated by Evans blue dye extravasation) and gastric content of inflammatory cytokine; tumor necrosis factor-alpha (TNF-alpha). Moreover, oxidative stress was increased as indicated by elevated lipid peroxides formation (measured as thiobarbituric acid reactive substances) and depleted reduced glutathione in gastric tissues. NF-kappaB translocation was also detected by electrophoretic mobility shift assay. Microscopically, gastric tissues subjected to I/R injury showed ulceration, hemorrhages, and neutrophil infiltration. Immunohistochemical studies of gastric sections revealed increased expression of p53 and Bcl-2 proteins. PDTC pretreatment reduced Evans blue extravasation, serum lactate dehydrogenase levels, gastric TNF-alpha levels, and thiobarbituric acid reactive substances content, and increased gastric glutathione content. Moreover, PDTC pretreatment abolished p53 expression and inhibited NF-kappaB translocation. Finally, histopathological changes were nearly restored by PDTC pretreatment. These results clearly demonstrate that NF-kappaB activation and pro-apoptotic protein p53 induction are involved in gastric I/R injury. PDTC protects against gastric I/R injury by an antioxidant, NF-kappaB inhibition, and by reduction of pro-apoptotic protein p53 expression, which seems to be downstream to NF-kappaB, thus promoting cell survival.     

AT1 receptor participates in the cardiac hypertrophy induced by resistance training in rats

Resistance training is accompanied by cardiac hypertrophy, but the role of the renin-angiotensin system (RAS) in this response is elusive. We evaluated this question in 36 male Wistar rats divided into six groups: control (n=6); trained (n=6); control+losartan (10 mg.kg(-1).day(-1), n=6); trained+losartan (n=6); control+high-salt diet (1%, n=6); and trained+high-salt diet (1%, n=6). High salt was used to inhibit the systemic RAS and losartan to block the AT1 receptor. The exercise protocol consisted of: 4x12 bouts, 5x/wk during 8 wk, with 65-75% of one repetition maximum. Left ventricle weight-to-body weight ratio increased only in trained and trained+high-salt diet groups (8.5% and 10.6%, P<0.05) compared with control. Also, none of the pathological cardiac hypertrophy markers, atrial natriuretic peptide, and alphaMHC (alpha-myosin heavy chain)-to-betaMHC ratio, were changed. ACE activity was analyzed by fluorometric assay (systemic and cardiac) and plasma renin activity (PRA) by RIA and remained unchanged upon resistance training, whereas PRA decreased significantly with the high-salt diet. Interestingly, using Western blot analysis and RT-PRC, no changes were observed in cardiac AT2 receptor levels, whereas the AT1 receptor gene (56%, P<0.05) and protein (31%, P<0.05) expressions were upregulated in the trained group. Also, cardiac ANG II concentration evaluated by ELISA remained unchanged (23.27+/-2.4 vs. 22.01+/-0.8 pg/mg, P>0.05). Administration of a subhypotensive dose of losartan prevented left ventricle hypertrophy in response to the resistance training. Altogether, we provide evidence that resistance training-induced cardiac hypertrophy is accompanied by induction of AT1 receptor expression with no changes in cardiac ANG II, which suggests a local activation of the RAS consistent with the hypertrophic response.     

Effects of spironolactone and eprosartan on cardiac remodeling and angiotensin-converting enzyme isoforms in rats with experimental heart failure

Angiotensin-converting enzyme (ACE)-2 is a newly described enzyme with antagonistic effects to those of the classical ACE (ACE-1). Both ANG II and aldosterone play an important role in the pathophysiology of congestive heart failure (CHF) and in the adverse cardiac remodeling during its development. In this study, we examined the effects of experimental CHF induced by an aortocaval fistula (ACF) and of its treatment with ANG II and aldosterone inhibitors on the relative levels of ACE-1 and ACE-2. We also compared the effects of spironolactone, an aldosterone antagonist, and eprosartan, an ANG II receptor antagonist, on heart hypertrophy and fibrosis in rats with ACF. Spironolactone (15 mg x kg(-1) x day(-1) ip, via minipump) or eprosartan (5 mg x kg(-1) x day(-1) ip, via minipump) was administered into rats with ACF for 14 and 28 days. Specific antibodies were used to determine the protein levels of myocardial ACE-1 and ACE-2. ACF increased the cardiac levels of ACE-1 and decreased those of ACE-2. Heart-to-body weight ratio significantly increased from 0.30 +/- 0.004% in sham-operated controls to 0.50 +/- 0.018% and 0.56 +/- 0.044% (P < 0.001) in rats with ACF, 2 and 4 wk after surgery, respectively, in association with increased plasma levels of aldosterone. The area occupied by collagen increased from 2.33 +/- 0.27% to 6.85 +/- 0.65% and 8.03 +/- 0.93% (P < 0.01), 2 and 4 wk after ACF, respectively. Both spironolactone and eprosartan decreased cardiac mass and collagen content and reversed the shift in ACE isoforms. ACF alters the ratio between ACE isoforms in a manner that increases local ANG II and aldosterone levels. Early treatment with both ANG II and aldosterone antagonists is effective in reducing this effect. Thus ACE isoform shift may represent an important component of the development of cardiac remodeling in response to hemodynamic overload, and its correction may contribute to the beneficial therapeutic effects of renin-angiotensin-aldosterone system inhibitors.     

Characterization of right ventricular function after monocrotaline-induced pulmonary hypertension in the intact rat

We characterized hemodynamics and systolic and diastolic right ventricular (RV) function in relation to structural changes in the rat model of monocrotaline (MCT)-induced pulmonary hypertension. Rats were treated with MCT at 30 mg/kg body wt (MCT30, n = 15) and 80 mg/kg body wt (MCT80, n = 16) to induce compensated RV hypertrophy and RV failure, respectively. Saline-treated rats served as control (Cont, n = 13). After 4 wk, a pressure-conductance catheter was introduced into the RV to assess pressure-volume relations. Subsequently, rats were killed, hearts and lungs were rapidly dissected, and RV, left ventricle (LV), and interventricular septum (IVS) were weighed and analyzed histochemically. RV-to-(LV + IVS) weight ratio was 0.29 +/- 0.05 in Cont, 0.35 +/- 0.05 in MCT30, and 0.49 +/- 0.10 in MCT80 (P < 0.001 vs. Cont and MCT30) rats, confirming MCT-induced RV hypertrophy. RV ejection fraction was 49 +/- 6% in Cont, 40 +/- 12% in MCT30 (P < 0.05 vs. Cont), and 26 +/- 6% in MCT80 (P < 0.05 vs. Cont and MCT30) rats. In MCT30 rats, cardiac output was maintained, but RV volumes and filling pressures were significantly increased compared with Cont (all P < 0.05), indicating RV remodeling. In MCT80 rats, RV systolic pressure, volumes, and peak wall stress were further increased, and cardiac output was significantly decreased (all P < 0.05). However, RV end-systolic and end-diastolic stiffness were unchanged, consistent with the absence of interstitial fibrosis. MCT-induced pressure overload was associated with a dose-dependent development of RV hypertrophy. The most pronounced response to MCT was an overload-dependent increase of RV end-systolic and end-diastolic volumes, even under nonfailing conditions.     

Narcotic antagonist-induced hypotension in the spontaneously hypertensive rat

Intravenous naloxone or naltrexone produced transient, dose-related reductions in the mean arterial pressure (MAP) and heart rate (HR) of urethane-anesthetized spontaneously hypertensive rats (SHRs). Yet these same doses of narcotic antagonists reduced HR but not MAP of normotensive Wistar-Kyoto rats (WKYs). Such effects were not observed upon administration to SHRs of increasing doses of methylnaltrexone, which possesses no central activity. (+)-Naloxone, which does not block opiate receptors, reduced HR but not MAP of both SHRs and WKYs. These findings indicate that SHRs and WKYs differ in their MAP and HR responses to narcotic antagonists. The high doses required for effect plus the brevity of the responses suggest that these drug effects are perhaps not mu-opiate receptor-mediated; however, the methylnaltrexone and (+)-naloxone findings clearly implicate a central specificity of action. We conclude that narcotic antagonist-induced changes in MAP and HR in SHRs are possibly specific and central in origin yet not mediated by mu-opiate receptors.     

Chronic administration of hexarelin attenuates cardiac fibrosis in the spontaneously hypertensive rat

Cardiac fibrosis is a hallmark of heart disease and plays a vital role in cardiac remodeling during heart diseases, including hypertensive heart disease. Hexarelin is one of a series of synthetic growth hormone secretagogues (GHSs) possessing a variety of cardiovascular effects via action on GHS receptors (GHS-Rs). However, the role of hexarelin in cardiac fibrosis in vivo has not yet been investigated. In the present study, spontaneously hypertensive rats (SHRs) were treated with hexarelin alone or in combination with a GHS-R antagonist for 5 wk from an age of 16 wk. Hexarelin treatment significantly reduced cardiac fibrosis in SHRs by decreasing interstitial and perivascular myocardial collagen deposition and myocardial hydroxyproline content and reducing mRNA and protein expression of collagen I and III in SHR hearts. Hexarelin treatment also increased matrix metalloproteinase (MMP)-2 and MMP-9 activities and decreased myocardial mRNA expression of tissue inhibitor of metalloproteinase (TIMP)-1 in SHRs. In addition, hexarelin treatment significantly attenuated left ventricular (LV) hypertrophy, LV diastolic dysfunction, and high blood pressure in SHRs. The effect of hexarelin on cardiac fibrosis, blood pressure, and cardiac function was mediated by its receptor, GHS-R, since a selective GHS-R antagonist abolished these effects and expression of GHS-Rs was upregulated by hexarelin treatment. In summary, our data demonstrate that hexarelin reduces cardiac fibrosis in SHRs, perhaps by decreasing collagen synthesis and accelerating collagen degradation via regulation of MMPs/TIMP. Hexarelin-reduced systolic blood pressure may also contribute to this reduced cardiac fibrosis in SHRs. The present findings provided novel insights and underscore the therapeutic potential of hexarelin as an antifibrotic agent for the treatment of cardiac fibrosis.     

Effect of regular voluntary exercise on resting cardiovascular responses in SHR and WKY pregnant rats.

The purpose of this study was to assess the influence of regular voluntary exercise in pregnant normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats on 1) uteroplacental perfusion and mean arterial pressure in the resting conscious condition and 2) fetal number, fetal weight, and number of fetal resorptions. WKYs and SHRs were randomly assigned to standard cages [CWKY (n = 10); CSHR (n = 6)] or cages with activity wheels [EWKY (n = 7); ESHR (n = 8)]. EWKYs and ESHRs exercised for 12 wk, and then all rats were bred and experiments were conducted on gestational day 17. Resting blood flow (microspheres), heart rate (HR), and mean arterial pressure (Pa) were measured. No significant difference was found in Pa, HR, uterine blood flow (ESHRs 52 +/- 8 ml.min-1.100 g-1; CSHRs 28 +/- 6 ml.min-1.100 g-1), or maternal placental blood flow (ESHRs, 122 +/- 31 ml.min-1.100 g-1; CSHRs 78 +/- 21 ml.min-1.100 g-1) among the groups. Exercise altered the relationship between maternal placental and uterine blood flow and Pa in the SHR; SHRs with lower Pa maintained higher placental and uterine blood flow after training. Before gestation ESHRs ran on average more kilometers per week than EWKYs (43 +/- 3 vs. 34 +/- 4), but during gestation ESHRs averaged fewer kilometers per week than EWKYs (16 +/- 4 vs. 22 +/- 4). Succinate dehydrogenase activity was higher in the white vastus lateralis (1.02 +/- 0.2 mumol cytochrome c reduced.min-1.g wet wt-1) and vastus intermedius (3.1 +/- 0.5 mumol cytochrome c reduced.min-1.g wet wt-1) muscles of ESHRs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diphenyleneiodonium sulfate, an NADPH oxidase inhibitor, prevents early alcohol-induced liver injury in the rat

The oxidant source in alcohol-induced liver disease remains unclear. NADPH oxidase (mainly in liver Kupffer cells and infiltrating neutrophils) could be a potential free radical source. We aimed to determine if NADPH oxidase inhibitor diphenyleneiodonium sulfate (DPI) affects nuclear factor-kappaB (NF-kappaB) activation, liver tumor necrosis factor-alpha (TNF-alpha) mRNA expression, and early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-16 g. kg(-1). day(-1)) continuously for up to 4 wk, using the Tsukamoto-French intragastric enteral feeding protocol. DPI or saline vehicle was administered by subcutaneous injection for 4 wk. Mean urine ethanol concentrations were similar between the ethanol- and ethanol plus DPI-treated groups. Enteral ethanol feeding caused severe fat accumulation, mild inflammation, and necrosis in the liver (pathology score, 4.3 +/- 0.3). In contrast, DPI significantly blunted these changes (pathology score, 0.8 +/- 0.4). Enteral ethanol administration for 4 wk also significantly increased free radical adduct formation, NF-kappaB activity, and TNF-alpha expression in the liver. DPI almost completely blunted these parameters. These results indicate that DPI prevents early alcohol-induced liver injury, most likely by inhibiting free radical formation via NADPH oxidase, thereby preventing NF-kappaB activation and TNF-alpha mRNA expression in the liver.