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We investigated the effects of the hydrogen sulfide (H₂S)-releasing derivatives of aspirin (ACS14) and salicylic acid (ACS21) in a rat model of metabolic syndrome induced by glutathione (GSH) depletion, causing hypertension and other pathological cardiovascular alterations. GSH depletion was induced in normal rats by the GSH-synthase inhibitor buthionine sulfoximine (BSO, 30 mmol/L day for seven days in the drinking water). Systolic blood pressure and heart rate were measured daily by the tail-cuff method, and plasma thromboxane B₂, 6-keto-prostaglandin F(2α), 8-isoprostane, GSH, insulin and glucose were determined at the end of the seven-day BSO schedule. In addition, ischemia/reperfusion-induced myocardial dysfunction and endothelial dysfunction were assayed on isolated heart and aortic rings, respectively. Unlike aspirin and salicylic acid, ACS14 and ACS21 reduced BSO-induced hypertension, also lowering plasma levels of thromboxane B₂, 8-isoprostane and insulin, while GSH remained in the control range. Neither ACS14 nor ACS21 caused gastric lesions. Both restored the endothelial dysfunction observed in aortic rings from BSO-treated rats, and in ischemia/reperfusion experiments they lowered left ventricular end-diastolic pressure, consequently improving the developed pressure and the maximum rise and fall of left ventricular pressure. Together with this improvement of heart mechanics there were reductions in the activity of creatine kinase and lactate dehydrogenase in the cardiac perfusate. This implies that H₂S released by both ACS14 and ACS21 was involved in protecting the heart from ischemia/reperfusion, and significantly limited vascular endothelial dysfunction in aortic tissue and the related hypertension., (Copyright © 2010 Elsevier B.V. All rights reserved.)

This study investigated whether oral simvastatin and manidipine interact in protecting the perfused rat heart from ischemia-reperfusion damage. Simvastatin (0.3 to 3 mg/kg) and manidipine (1 to 10 mg/kg) were given orally singly or together to normocholesterolemic rats once a day for seven consecutive days. At the end of treatment, systolic blood pressure and heart rate were measured in conscious rats, and the lipid profile and other biochemical markers, such as thromboxane B(2), nitrite/nitrates and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)) were determined in the plasma. Hearts were then isolated, perfused with Krebs-Henseleit, and subjected to low flow ischemia-reperfusion injury. Post-ischemic recovery of left ventricular function was measured as left ventricular developed pressure and left ventricular end-diastolic pressure. Creatine kinase, lactate dehydrogenase, tumor necrosis factor-alpha and 6-keto-PGF(1alpha) were measured in the heart effluents. In conscious animals, simvastatin alone increased plasma 6-keto-PGF(1alpha) release while manidipine alone reduced systolic blood pressure with a slight sympathetic reflex increase in heart rate, and increased plasma nitrite/nitrates. The combined treatment produced the same effects, but significantly more marked, and accompanied by a significant reduction of thromboxane B(2). Combined treatment was also significantly more effective than the single drugs in protecting the hearts from ischemia-reperfusion injury, with inhibition of creatine kinase, lactate dehydrogenase and tumor necrosis factor-alpha, and enhancement of 6-keto-PGF(1alpha) during reperfusion. These data show that simvastatin and manidipine interact positively in protecting the rat heart from ischemia-reperfusion injury, possibly through increased prostaglandin and nitric oxide formation by the vascular endothelial cells.

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) inhibitor recognized as an independent risk factor for endothelial dysfunction and coronary heart diseases. This study investigated whether ADMA (10 mg/kg day for 14 days) affected endothelial function and aggravated post-ischemic ventricular dysfunction in the perfused rat heart. Systolic blood pressure and heart rate, plasma levels of ADMA and nitrite/nitrate were measured in vehicle- and ADMA-treated rats. Perfused hearts were submitted to global ischemia-reperfusion and vascular endothelial dysfunction was examined with angiotensin II in coronary vessels and aortic rings. Endothelial NO synthase (eNOS) and angiotensin-converting enzyme (ACE) mRNA expression in aortic and cardiac tissues were measured. ADMA-treated rats had higher systolic blood pressure (1.3-fold, P<0.01) and slower heart rate (16%, P<0.05) than controls. Plasma ADMA rose (1.9-fold, P<0.01) and nitrite/nitrate concentration decreased 59% (P<0.001). Ventricular contraction (stiffness) increased significantly, with worsening of post-ischemic ventricular dysfunction. In preparations from ADMA-treated rats the coronary vasculature's response to angiotensin II was almost doubled (P<0.01) and the maximal vasorelaxant effect of acetylcholine in aortic rings was significantly lower than in preparations from vehicle-treated rats. In cardiac and aortic tissues eNOS mRNA and ACE mRNA levels were similar in controls and ADMA-treated rats. The increased plasma levels of ADMA presumably cause endothelial dysfunction because of a deficiency in NO production, which also appears involved in the aggravation of myocardial ischemia-reperfusion injury.

Male Sprague-Dawley rats given N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 8 weeks showed: (1) a clear-cut increase in systolic blood pressure; (2) a consistent decrease of endothelial-cell nitric oxide synthase (eNOS) gene expression in aortic tissue; (3) a marked reduction of plasma nitrite/nitrate concentrations; (4) a reduction of the relaxant activity of acetylcholine (ACh, from 10(-10) to 10(-4) M) on norepinephrine-precontracted aortic rings (reduction by 48+/-5%); (5) a marked decrease (-58%) of the basal release of 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) from aortic rings. In L-NAME-treated rats, administration in the last 4 weeks of either the angiotensin-converting enzyme (ACE) inhibitor enalapril (10 mg/kg/day in tap water) or the angiotensin AT(1)-receptor antagonist losartan (10 mg/kg/day in tap water) decreased systolic blood pressure levels, completely restored eNOS mRNA levels in aortic tissue and plasma nitrite/nitrate levels, and allowed a consistent recovery of both the relaxant activity of acetylcholine and the generation of 6-keto-PGF1alpha. Coadministration of icatibant, a bradykinin B(2)-receptor antagonist (200 microg/kg/day), with enalapril blunted the stimulatory effect of the ACE inhibitor on eNOS mRNA expression, circulating levels of nitrite/nitrate, the relaxant activity of ACh and the release of 6-keto-PGF1alpha in L-NAME-treated rats. The generation of 6-keto-PGF1alpha from aortic rings was also decreased in rats coadministered icatibant with losartan. These findings indicate that (1) the ACE inhibitor enalapril and the angiotensin AT(1)-receptor blocker losartan are equally effective to reverse NAME-induced endothelial dysfunction; (2) the beneficial effect of enalapril on the endothelial vasodilator function in L-NAME-treated rats is mediated by bradykinin B(2)-receptor activation; and (3) the enhanced endothelial generation of prostacyclin induced by losartan in L-NAME rats is also mediated by bradykinin B(2)-receptor activation.

The aim of this study was to investigate the capacity of the 2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester (NCX 4016), a nitric oxide (NO)-releaser derivative of aspirin, to decrease blood pressure in spontaneously hypertensive rats (SHR) and to counteract the adrenergic vasoconstriction in perfused tail artery of these animals. Oral treatment for 10 consecutive days with NCX 4016 (100 micromol/kg) in SHR and their genetic controls Wistar Kyoto (WKY) rats resulted in a reduction of blood pressure in SHR but not in WKY rats. In SHR, the NCX 4016 treatment increased the serum nitrite/nitrate and diminished the serum thromboxane B2, whereas aspirin did not change blood pressure but abolished the serum thromboxane B2. Perfused tail arteries excised from vehicle-treated SHR exhibited a significant impairment of endothelium-dependent vasorelaxant function. These vessels, prepared from SHR or WKY rats treated orally with NCX 4016 (10, 30 and 100 micromol/kg for 7 consecutive days), revealed a dose-dependent decrease in vasoconstriction in response to transmural nerve stimulation and norepinephrine, whereas aspirin was ineffective. Furthermore, in tail arteries of both SHR and WKY rats treated orally with NCX 4016 (100 micromol/kg for 7 consecutive days), the cGMP increased significantly. In conclusion, NCX 4016, by releasing NO and increasing cGMP in vascular tissue, reduces sympathetic-mediated vasoconstriction in resistance vessels and lowers blood pressure in SHR.

Endothelial dysfunction ensuing inhibition of nitric oxide synthase (NOS) was investigated in male Sprague-Dawley rats given N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 8 weeks. Age-matched rats served as controls. L-NAME-treated rats, as compared to control animals, showed: (1) a clear-cut increase in systolic blood pressure; (2) a consistent decrease of endothelial-cell NOS (eNOS) gene expression in aortic tissue; (3) a reduction of the relaxant activity of acetylcholine (ACh, from 10(-10) to 10(-4) M) on norepinephrine-precontracted aortic rings (reduction by 52+/-5%); (4) a marked decrease (-50%) of the basal release of 6-keto-prostaglandin F(1 alpha) (6-keto-PGF(1 alpha)) from aortic rings. In L-NAME-treated rats, administration in the last 2 weeks of either the angiotensin-converting enzyme inhibitor enalapril (1 mg/kg/day) or the cognate drug quinapril (1 mg/kg/day) decreased systolic blood pressure levels, completely restored eNOS mRNA levels in aortic tissue, and allowed a consistent recovery of both the relaxant activity of ACh and the generation of 6-keto-PGF(1 alpha). No difference was present in the ability of the two angiotensin-converting enzyme inhibitors to reverse NAME-induced endothelial dysfunction. These findings indicate that L-NAME-induced hypertension in the rat relies on the marked impairment of the endothelial vasodilator function, with an ensuing contribution by a decreased production of prostacyclin by the endothelial cells. Angiotensin-converting enzyme inhibition by enalapril or quinapril was equally effective in improving endothelial vasodilator function, prostacyclin endothelial production and restoring aortic eNOS mRNA.

The ability of hexarelin, an effective growth hormone (GH)-releasing hexapeptide, to reverse the worsening of cardiac dysfunction in GH-deficient animals was studied in young male rats passively immunized by administration of an anti-GH-releasing hormone (GHRH) serum. Heart preparations from anti-GHRH serum-treated rats, undergoing low-flow ischemia and reperfusion, showed: (1) a progressive increase of left ventricular end-diastolic pressure during the ischemic period and a poor recovery of contractility at reperfusion with a consistent decrease of the left ventricular-developed pressure; (2) a decreased rate of formation of 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), a stable metabolite of prostacyclin, in perfusates from preischemic and reperfusion periods; (3) an increased vasopressor activity of angiotensin II. Hexarelin (80 microg/kg, bid, s.c.), administered for 15 days to anti-GHRH serum-treated rats, restored to normal the impaired somatotropic function and counteracted the ischemic damage, improving postischemic left ventricular developed pressure to values higher than those of controls. Furthermore, both the generation of 6-keto-PGF1alpha and the vasopressor activity of angiotensin II reverted to those of control preparations. Administration of hexarelin to control rats induced a considerable improvement of postischemic ventricular function of the perfused hearts which was similar to that present in preparations from anti-GHRH serum-treated rats given hexarelin. This protective activity was divorced from any further stimulation of somatotropic function. Collectively, these data indicate that, in GH-deficient rats, hexarelin is capable of restoring somatotropic function and has a beneficial effect in myocardial ischemia and reperfusion damage. In addition, the increased responsiveness of the coronary vasculature to angiotensin II and the decreased generation of prostacyclin in hearts from GH-deficient rats would indicate that for prevention of injury and dysfunction of the vascular endothelium a normal somatotropic function is mandatory.

In these experiments rats were exposed to hyperbaric oxygen (100% oxygen; 2.5 atmospheres absolute pressure) for 1, 3 or 6 h. At the end of these periods the hearts were removed and subjected to low flow ischemia (perfusion rate from 12 ml/min to 2 ml/min for 40 min) and reperfusion. Hearts excised from control rats were subjected to the same procedure of ischemia and reperfusion. The data obtained from these experiments clearly indicate that the ischemic picture observed in control hearts is worsened in hearts obtained from hyperbaric oxygen-exposed animals. In fact, after ventricular standstill of the ischemic phase, the left ventricular end-diastolic pressure increased significantly and proportionally according to the time of hyperbaric oxygen exposure. The vasopressor activity of angiotensin II on coronary perfusion pressure was significantly changed, as compared to that in the control preparation: these alterations, well correlated to the time of hyperbaric oxygen exposure, seem to suggest impairment of the vascular endothelium-dependent relaxant function. Furthermore N-acetylcysteine and defibrotide, given orally to the rats before hyperbaric oxygen exposure, prevented the aggravation of the ischemic damage induced in ex vivo hearts.

The effects of growth hormone (GH) deficiency on cardiac function were studied in young male rats administered an anti-GH-releasing hormone (GHRH) serum from postnatal day 20 to 40. Dependence of heart abnormalities on GH deficiency was ascertained by giving a group of anti-GHRH serum-treated rats GH replacement therapy. Heart preparations from anti-GHRH serum-treated rats, undergoing low-flow ischemia, showed a progressive increase in left ventricular end-diastolic pressure with poor recovery of mechanical activity and increased coronary perfusion pressure upon reperfusion. Hearts from anti-GHRH serum + GH-treated rats, undergoing global reduction to the flow, showed only a minimal increase of left ventricular end-diastolic pressure and, upon reperfusion, cardiac mechanical activity recovered almost completely. Similar findings were also observed in heart preparations from control (normal rabbit serum-treated) rats. Infusion of acetylcholine (10(-6) M) into heart preparations in the preischemic period increased coronary perfusion pressure values more markedly in hearts from normal rabbit serum- and anti-GHRH serum + GH-treated rats than in those from anti-GHRH serum-treated rats. These results indicate that selective GH deficiency in young male rats renders the heart more sensitive to ischemic damage and leads to an impairment of cardiac muscarinic receptor function.

In a first set of experiments, we evaluated the effects of different doses (5.0, 10, 20 and 40 mg/kg p.o.) of carbamazepine on nociceptive thresholds to thermal and mechanical stimuli, and on paw inflammatory hyperalgesia induced by the injection of brewer's yeast. Moreover, we studied the effect of carbamazepine on paw inflammatory edema by plethysmometry. Carbamazepine did not modify nociceptive latencies, but dose dependently reduced the hyperalgesia and the edema induced by the brewer's yeast injection in the rat hindpaw. In a second set of experiments, we studied the effects induced by the same doses of the drug on subcutaneous carrageenin-induced inflammation. Carbamazepine dose dependently reduced the inflammatory exudate, the prostaglandin E2-like activity in the exudate, and the substance P concentrations in the exudate. Our results demonstrate that carbamazepine is able to inhibit the development of different types of inflammation in the rat.

Isoproterenol and salbutamol caused relaxation of guinea-pig trachea, and generation of PGE2. The phenomenon appears to be specific for beta-adrenergic agonists since the relaxant activity induced by atropine, theophylline and papaverine was not associated with generation of prostaglandin-like material from tracheal smooth muscles. Indomethacin reduced only slightly the relaxation of the tracheal tissue induced by isoproterenol and salbutamol. The possibility is discussed that the increased arachidonic acid metabolism during trachea beta-adrenergic relaxation represents a metabolic event involving phospholipid methylation and membrane fluidity.

Defibrotide, a polydeoxyribonucleotide obtained from mammalian lungs, reduced in a dose-dependent fashion the ischemic contracture due to low perfusion (0.2 ml/min) of isovolumic left heart of rabbit and abolished the irregular rhythm of the heart, thereby restoring the cardiomechanical activity upon reperfusion (20 ml/min). Defibrotide stimulated the release of PG-like material from the heart in a dose-dependent manner without modifying the basal contractility. Both PGE2 and PGI2 (10 ng/ml) have an antiischemic activity on this preparation as shown by the partial reduction of the ischemic contracture and by the improvement of heart contractility upon reperfusion. Indomethacin infusion (1 microgram/ml) completely removed both the antiischemic activity of Defibrotide (400 micrograms/ml) and its ability to increase the generation of prostaglandins in the rabbit heart. These results suggest that Defibrotide has a beneficial influence on ischemic rabbit heart through an increase in prostaglandin synthesis. However other mechanisms not necessarily related to prostaglandin generation, such as a direct effect on membrane function deactivation and mitochondrial Ca2+ overload, should be considered in explaining the antiischemic activity of Defibrotide in the rabbit heart.

Various doses of histamine, bradykinin and leukotriene C4 caused bronchoconstriction in anaesthetized guinea-pigs which were breathing spontaneously or artificially ventilated; there was a simultaneous, dose-related increase in circulating TXA2. The animals were prepared for continuous recording of extracorporeal circulation in order to detect the appearance in the blood of bioassayable levels of TXA2 -like substance. Furthermore, a TXA2 derivative, the mono-O-Me-TXB2, was radioimmunoassayed. Atropine, oxytropium bromide and ipratropium bromide given in mumol doses prevented both the increased airway resistance and the release of TXA2-like substance in the blood Pirenzepine dihydrochloride was the least active of the drugs tested. The protecting activity of anticholinergics and the relationship with their ability to affect TXA2-like substance generation suggest a new site of action for these drugs besides the blockade of muscarinic receptors.