Artificial phrenoesophageal ligament. An experimental study in dogs.

This report deals with the preparation of a 'true' artificial phrenoesophageal ligament aimed at restoring effective anchoring of the esophagus to the diaphragm, keeping the esophagogastric sphincter in the abdomen. A total of 24 mongrel dogs were assigned to four groups: (i) Group I (n = 4): the esophageal diaphragm hiatus left wide open; (ii) Group II (n = 8): the anterolateral esophagus walls were attached to the diaphragm by the artificial ligament and the esophageal hiatus was left wide opened; (iii) Group III (n = 5): in addition to the use of the artificial ligament, the esophageal hiatus was narrowed with two retroesophageal stitches; (iv) Group IV (n = 7): the only procedure was the esophageal hiatus narrowing with two retroesophageal stitches. The phrenoesophagogastric connections were released, sparing the vagus nerves. Five animals of groups III and IV, which did not develop hiatal hernia, were submitted to esophageal manometry immediately before and 15 days after surgery. In group I, all animals developed huge sliding hiatal hernias. In group II, two dogs (25%) had a paraesophageal hernia between the two parts of the artificial ligament. In group III, neither sliding hiatal hernia nor paraesophageal hernia occurred. In group IV, two animals (28.6%) developed sliding esophageal hiatus hernia. Regarding esophageal manometry, postoperative significant difference between groups III and IV (P = 0.008) was observed. Thus, the artificial phrenoesophageal ligament maintained the esophagus firmly attached to the diaphragm in all animals and the esophagogastric sphincter pressure was significantly higher in this group.

Activation of cytokines corroborate with development of inflammation and autoimmunity in thromboangiitis obliterans patients.

Thromboangiitis obliterans (TAO) is a segmental inflammatory occlusive disorder that affects the arm and leg arteries of young smokers. The immune system seems to play a critical role in the aetiology of TAO; however, knowledge of the aspects involved in the progression of vascular tissue inflammation and, consequently, the evolution of this disease is still limited. This study was carried out to investigate the cytokine levels of tumour necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-4, IL-17 and IL-23 in the plasma of TAO patients presenting with acute clinical manifestations. The study included 20 TAO patients (n = 10 women; n = 10 men) aged 38-59 years under clinical follow-up, classified into two groups: (i) TAO former smokers (n = 11) and (ii) TAO active smokers (n = 9); the control groups included normal volunteer non-smokers (n = 10, active smokers (n = 10) and former smokers (n = 10). Patients' plasma samples were measured using the sandwich enzyme-linked immunosorbent assay. Statistical analyses were performed using the non-parametric Mann-Whitney U-test, with parameters significant at P < 0·05. The activities of all cytokines were different in groups of TAO patients when compared with normal controls, and decreased for control smokers. Increased levels of TNF-α, IL-1ß, IL-4, IL-17 and IL-23 were significant in patients with TAO when compared to the controls (P < 0·005, all parameters). The results presented here indicate an increased production of cytokines in TAO, possibly contributing to the inflammatory response observed in the patients' vascular levels. In addition, the increased levels of IL-17 and IL-23 suggest that the disturbance of TAO is involved with mechanisms of autoimmunity. Thus, the discovery of IL-17 and its association with inflammation and autoimmune pathology has reshaped our viewpoint regarding the pathogenesis of TAO, which was based previously on the T helper type 1 (Th1)-Th2 paradigm.

Oral glutamine dipeptide or oral glutamine free amino acid reduces burned injury progression in rats.

This study was carried out to evaluate the effect of Glutamine, as a dipeptide or a free amino acid form, on the progression of burn injuries in rats. Thirty male Wistar rats were burned with a comb metal plate heated in boiling water (98 °C) for three minutes, creating four rectangular full-thickness burn areas separated by three unburned interspaces (zone of stasis) in both dorsum sides. The animals were randomized into three groups (n=10): saline solution (G1-Control) and treated groups that orally received Glutamine as dipeptide (G2-Dip) or free amino acid (G3-FreeAA). Two and seven days after burn injury, lesions were photographed for unburned interspaces necrosis evolution assessment. Seven days after injury, glutathione seric was measured and histopathological analysis was performed. By photographs, there was a significant reduction in necrosis progression in G3-Free-AA between days two and seven. Histopathological analysis at day 7 showed a significantly higher stasis zone without necrosis and a higher number of fibroblasts in G2-Dip and G3-FreeAA compared with G1-Control. Also, glutathione serum dosage was higher in G2-Dip. The plasmatic glutathione levels were higher in the G2-Dip than the G1-Control, and there was a trend to higher levels in G3-FreeAA. The reduction in histological lesions, greater production of fibroblasts, and greater amounts of glutathione may have benefited the evolution of burn necrosis, which showed greater preservation of interspaces.

Determination of kininogens levels and kallikrein/kininase II activities in patients with thromboangiitis obliterans.

Some components of the kinin system such as plasma kallikrein levels, the activities of tissue kallikrein (including saliva) and kininase II and the concentrations of kininogen fractions (low-molecular weight/LKg and high-molecular weight/HKg) were evaluated in the plasma of patients with thromboangiitis obliterans (TAO) presenting clinical symptoms of the condition. Twenty TAO were diagnosed by means of the traditional Shionoya and Olin criteria and later classified into non-smokers (n = 11) and active smokers (n = 9). Fifty-three normal, non-smoking/smoking individuals (control) were also studied. Kininogen levels were determined by ELISA; the activities of kallikreins and kininase II were determined using selective substrates. The levels of enzymes (kallikreins and kininase II) and protein (kininogens) were significantly higher in patients with TAO who were active smokers compared to the control groups (no matter whether control individuals were active smokers or non-smokers, P < 0.001 for all comparisons). Interestingly, regardless of the time of disease onset, a significant increase in the levels of these components of the kinin system was also observed in patients when TAO active smokers were compared with TAO ex-smokers (P < 0.01 for all analysed parameters). Activation of the kinin system in patients with TAO may indicate the involvement of vasodilatation in an attempt to control vascular changes, thereby favouring the deposition of immune complexes at the vascular level because of nicotine stimulation. Moreover, our results corroborate the idea that TAO can be an autoimmune disorder with specific mechanisms.

Extracellular alkalinization induces endothelium-derived nitric oxide dependent relaxation in rat thoracic aorta.

AIM: To investigate the mechanism through which the extracellular alkalinization promotes relaxation in rat thoracic aorta. METHODS: The relaxation response to NaOH-induced extracellular alkalinization (7.4-8.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M). The vascular reactivity experiments were performed in endothelium-intact and -denuded rings, in the presence or and absence of indomethacin (10(-5) M), NG-nitro-l-arginine methyl ester (L-NAME, 10(-4) M), N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide/HCl (W-7, 10(-7) M), 2,5-dimethylbenzimidazole (DMB, 2×10(-5) M) and methyl-ß-cyclodextrin (10(-2) M). In addition, the effects of NaOH-induced extracellular alkalinization (pH 8.0 and 8.5) on the intracellular nitric oxide (NO) concentration was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5 µM), in the presence and absence of DMB (2×10(-5) M). RESULTS: The extracellular alkalinization failed to induce any change in vascular tone in aortic rings pre-contracted with KCl. In rings pre-contracted with Phe, the extracellular alkalinization caused relaxation in the endothelium-intact rings only, and this relaxation was maintained after cyclooxygenase inhibition; completely abolished by the inhibition of nitric oxide synthase (NOS), Ca(2+)/calmodulin and Na(+)/Ca(2+) exchanger (NCX), and partially blunted by the caveolae disassembly. CONCLUSIONS: These results suggest that, in rat thoracic aorta, that extracellular alkalinization with NaOH activates the NCX reverse mode of endothelial cells in rat thoracic aorta, thereby the intracellular Ca(2+) concentration and activating the Ca(2+)/calmodulin-dependent NOS. In turn, NO is released promoting relaxation.

Effects of NO/cGMP inhibitors in a rat model of anaphylactoid shock.

Anaphylactic shock can be defined as an acute syndrome, and it is the most severe clinical manifestation of allergic diseases. Anaphylactoid reactions are similar to anaphylactic events but differ in the pathophysiological mechanism. Nitric oxide (NO) inhibitors during anaphylaxis suggest that NO might decrease the signs and symptoms of anaphylaxis but exacerbate associated vasodilation. Therefore, blocking the effects of NO on vascular smooth muscle by inhibiting the guanylate cyclase (GC) would be a reasonable strategy. This study aimed to investigate the effects of NO/cGMP pathway inhibitors methylene blue (MB), Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and indigo carmine (IC) in shock induced by compound 48/80 (C48/80) in rats. The effect was assessed by invasive blood pressure measurement. Shock was initiated by C48/80 intravenous bolus injection 5 min before (prophylactic) or after (treatment) the administration of the inhibitors MB (3 mg/kg), L-NAME (1 mg/kg), and IC (3 mg/kg). Of the groups that received drugs as prophylaxis for shock, only the IC group did not present the final systolic blood pressure (SBP) better than the C48/80 group. Regarding shock treatment with the drugs tested, all groups had the final SBP similar to the C48/80group. Altogether, our results suggested that inhibition of GC and NO synthase in NO production pathway was not sufficient to revert hypotension or significantly improve survival.

Use of alprostadil, a stable prostaglandin E1 analogue, for the attenuation of rat skeletal muscle ischemia and reperfusion injury.

AIM: Some stable prostaglandin analogues such as alprostadil have been used to attenuate the deleterious effects of ischemia and reperfusion injury. The aim of this paper was to test if alprostadil can decrease the ischemia- reperfusion injury in rat skeletal muscle using muscular enzymes as markers, such as aspartate aminotransferase (AST), creatine kinase (CPK), lactate dehydrogenase (LDH); degeneration products of cell membrane-malondialdehyde (MDA) and muscle glycogen storage. METHODS: Thirty male Wistar rats were used in a model of hind limb ischemia achieved by infrarenal aortic cross-clamping. The animals were randomized into three equal groups (N=10) submitted to 5 hours of ischemia followed by one hour of reperfusion. The first group (control) received continuous intravenous infusion of saline solution and the second group (preischemia, GPI) received continuous intravenous infusion of alprostadil throughout the experiment starting 20 minutes before the aortic cross-clamping. The third group, prereperfusion (GPR), received alprostadil only during the reperfusion period, with intravenous infusion being started 10 min before the clamp release. RESULTS: There was no difference in CPK, LDH, AST or tissue glycogen values between groups. However, a significant elevation in MDA was observed in the GPI and GPR groups compared to the control group, with no difference between the GPI and GPR. CONCLUSIONS: Under conditions of partial skeletal muscle ischemia, alprostadil did not reduce the release of muscular enzymes, the consumption of tissue glycogen or the effects of ischemia and reperfusion on the cell membrane, characterized by lipid peroxidation.

Oral glutamine dipeptide or oral glutamine free amino acid reduces burned injury progression in rats / O dipeptídeo de glutamina oral ou aminoácido livre de glutamina oral reduz a progressão da lesão por queimadura em ratos

Abstract This study was carried out to evaluate the effect of Glutamine, as a dipeptide or a free amino acid form, on the progression of burn injuries in rats. Thirty male Wistar rats were burned with a comb metal plate heated in boiling water (98 °C) for three minutes, creating four rectangular full-thickness burn areas separated by three unburned interspaces (zone of stasis) in both dorsum sides. The animals were randomized into three groups (n=10): saline solution (G1-Control) and treated groups that orally received Glutamine as dipeptide (G2-Dip) or free amino acid (G3-FreeAA). Two and seven days after burn injury, lesions were photographed for unburned interspaces necrosis evolution assessment. Seven days after injury, glutathione seric was measured and histopathological analysis was performed. By photographs, there was a significant reduction in necrosis progression in G3-Free-AA between days two and seven. Histopathological analysis at day 7 showed a significantly higher stasis zone without necrosis and a higher number of fibroblasts in G2-Dip and G3-FreeAA compared with G1-Control. Also, glutathione serum dosage was higher in G2-Dip. The plasmatic glutathione levels were higher in the G2-Dip than the G1-Control, and there was a trend to higher levels in G3-FreeAA. The reduction in histological lesions, greater production of fibroblasts, and greater amounts of glutathione may have benefited the evolution of burn necrosis, which showed greater preservation of interspaces.

Resumo Este estudo foi realizado para avaliar o efeito da Glutamina, como um dipeptídeo ou forma de aminoácido livre, na progressão de queimaduras em ratos. Trinta ratos Wistar machos foram queimados com um pente de metal aquecido em água fervente (98 °C) por três minutos, criando quatro áreas retangulares queimadas separadas por três interesespaços não queimados (zona de estase) em ambos os lados do dorso. Os animais foram randomizados em três grupos (n = 10): solução salina (G1-Controle) e grupos tratados que receberam glutamina via oral como dipeptídeo (G2-Dip) ou aminoácido livre (G3-FreeAA). Dois e sete dias após a queimadura, as lesões foram fotografadas para avaliação da evolução da necrose entre os espaços não queimados. Sete dias após a lesão, foi dosada a glutationa sérica e realizada análise histopatológica. Pelas fotografias, houve uma redução significativa na progressão da necrose no G3-Free-AA entre os dias dois e sete. A análise histopatológica no dia 7 mostrou uma zona de estase significativamente maior sem necrose e número mais elevado de fibroblastos em G2-Dip e G3-FreeAA em comparação com G1-Controle. Os níveis plasmáticos de glutationa foram maiores no G2-Dip em relação ao G1-Controle, e houve tendência a níveis mais elevados no G3-FreeAA. A redução das lesões histológicas, maior produção de fibroblastos, maior quantidade de glutationa podem ter beneficiado a evolução da necrose da queimadura, que mostrou maior preservação dos interespaços.

Oral glutamine dipeptide or oral glutamine free amino acid reduces burned injury progression in rats

Abstract This study was carried out to evaluate the effect of Glutamine, as a dipeptide or a free amino acid form, on the progression of burn injuries in rats. Thirty male Wistar rats were burned with a comb metal plate heated in boiling water (98 °C) for three minutes, creating four rectangular full-thickness burn areas separated by three unburned interspaces (zone of stasis) in both dorsum sides. The animals were randomized into three groups (n=10): saline solution (G1-Control) and treated groups that orally received Glutamine as dipeptide (G2-Dip) or free amino acid (G3-FreeAA). Two and seven days after burn injury, lesions were photographed for unburned interspaces necrosis evolution assessment. Seven days after injury, glutathione seric was measured and histopathological analysis was performed. By photographs, there was a significant reduction in necrosis progression in G3-Free-AA between days two and seven. Histopathological analysis at day 7 showed a significantly higher stasis zone without necrosis and a higher number of fibroblasts in G2-Dip and G3-FreeAA compared with G1-Control. Also, glutathione serum dosage was higher in G2-Dip. The plasmatic glutathione levels were higher in the G2-Dip than the G1-Control, and there was a trend to higher levels in G3-FreeAA. The reduction in histological lesions, greater production of fibroblasts, and greater amounts of glutathione may have benefited the evolution of burn necrosis, which showed greater preservation of interspaces.

Resumo Este estudo foi realizado para avaliar o efeito da Glutamina, como um dipeptídeo ou forma de aminoácido livre, na progressão de queimaduras em ratos. Trinta ratos Wistar machos foram queimados com um pente de metal aquecido em água fervente (98 °C) por três minutos, criando quatro áreas retangulares queimadas separadas por três interesespaços não queimados (zona de estase) em ambos os lados do dorso. Os animais foram randomizados em três grupos (n = 10): solução salina (G1-Controle) e grupos tratados que receberam glutamina via oral como dipeptídeo (G2-Dip) ou aminoácido livre (G3-FreeAA). Dois e sete dias após a queimadura, as lesões foram fotografadas para avaliação da evolução da necrose entre os espaços não queimados. Sete dias após a lesão, foi dosada a glutationa sérica e realizada análise histopatológica. Pelas fotografias, houve uma redução significativa na progressão da necrose no G3-Free-AA entre os dias dois e sete. A análise histopatológica no dia 7 mostrou uma zona de estase significativamente maior sem necrose e número mais elevado de fibroblastos em G2-Dip e G3-FreeAA em comparação com G1-Controle. Os níveis plasmáticos de glutationa foram maiores no G2-Dip em relação ao G1-Controle, e houve tendência a níveis mais elevados no G3-FreeAA. A redução das lesões histológicas, maior produção de fibroblastos, maior quantidade de glutationa podem ter beneficiado a evolução da necrose da queimadura, que mostrou maior preservação dos interespaços.

Prophylactic Use of Laser Light and Methylene Blue on Ischemia and Liver Reperfusion Injury.

OBJECTIVE: This study aimed to evaluate the effect of hepatic preconditioning with laser light in the presence of methylene blue (MB) in the liver ischemia-reperfusion injury process. METHOD: Forty male Wistar rats were divided into 8 experimental groups (n = 5). Saline (.5 mL) or MB (15 mg/kg) was injected intravenously (inferior vena cava). After 2 minutes, 660 nm laser light was applied at a dose of 112.5 DE. Fifteen minutes after the application of saline or MB, 1 hour partial ischemia followed by 15 minutes of reperfusion was applied when the rats were sacrificed. The mitochondrial function parameters (O2 consumption rates in states 3 and 4 and the respiratory control ratio), osmotic swelling, and determination of malondialdehyde were evaluated. Hepatic function was studied using the serum determination of the alanine aminotransferase and aspartate aminotransferase enzymes. RESULTS AND CONCLUSIONS: MB therapy alone showed the capacity of preserving the rate of oxygen consumption in the mitochondrial respiratory state of the group submitted to ischemia compared to the sham group. However, when combined with low-intensity laser therapy, it failed to replicate the relevant protective effects in relation to oxidative phosphorylation or the mitochondrial membrane ischemia/reperfusion injury. Whether or not MB was combined with laser treatment, it was shown to be efficient in reducing oxidative stress. In relation to alanine aminotransferase enzymes, whether or not laser treatment was combined with MB had a protective effect on the hepatic lesion, whereas in relation to aspartate aminotransferase enzymes only laser treatment was able to provide this protection.

Endothelium-dependent and -independent hepatic artery vasodilatation is not impaired in a canine model of liver ischemia-reperfusion injury.

We investigated whether hepatic artery endothelium may be the earliest site of injury consequent to liver ischemia and reperfusion. Twenty-four heartworm-free mongrel dogs of either sex exposed to liver ischemia/reperfusion in vivo were randomized into four experimental groups (N = 6): a) control, sham-operated dogs, b) dogs subjected to 60 min of ischemia, c) dogs subjected to 30 min of ischemia and 60 min of reperfusion, and d) animals subjected to 45 min of ischemia and 120 min of reperfusion. The nitric oxide endothelium-dependent relaxation of hepatic artery rings contracted with prostaglandin F2a and exposed to increasing concentrations of acetylcholine, calcium ionophore A23187, sodium fluoride, phospholipase-C, poly-L-arginine, isoproterenol, and sodium nitroprusside was evaluated in organ-chamber experiments. Lipid peroxidation was estimated by malondialdehyde activity in liver tissue samples and by blood lactic dehydrogenase (LDH), serum aspartate aminotransferase (AST) and serum alanine aminotransferase (ALT) activities. No changes were observed in hepatic artery relaxation for any agonist tested. The group subjected to 45 min of ischemia and 120 min of reperfusion presented marked increases of serum aminotransferases (ALT = 2989 +/- 1056 U/L and AST = 1268 +/- 371 U/L; P < 0.01), LDH = 2887 +/- 1213 IU/L; P < 0.01) and malondialdehyde in liver samples (0.360 +/- 0.020 nmol/mgPT; P < 0.05). Under the experimental conditions utilized, no abnormal changes in hepatic arterial vasoreactivity were observed: endothelium-dependent and independent hepatic artery vasodilation were not impaired in this canine model of ischemia/reperfusion injury. In contrast to other vital organs and in the ischemia/reperfusion injury environment, dysfunction of the main artery endothelium is not the first site of reperfusion injury.

Acute but not chronic metabolic acidosis potentiates the acetylcholine-induced reduction in blood pressure: an endothelium-dependent effect.

Metabolic acidosis has profound effects on vascular tone. This study investigated the in vivo effects of acute metabolic acidosis (AMA) and chronic metabolic acidosis (CMA) on hemodynamic parameters and endothelial function. CMA was induced by ad libitum intake of 1% NH4Cl for 7 days, and AMA was induced by a 3-h infusion of 6 M NH4Cl (1 mL/kg, diluted 1:10). Phenylephrine (Phe) and acetylcholine (Ach) dose-response curves were performed by venous infusion with simultaneous venous and arterial blood pressure monitoring. Plasma nitrite/nitrate (NOx) was measured by chemiluminescence. The CMA group had a blood pH of 7.15±0.03, which was associated with reduced bicarbonate (13.8±0.98 mmol/L) and no change in the partial pressure of arterial carbon dioxide (PaCO2). The AMA group had a pH of 7.20±0.01, which was associated with decreases in bicarbonate (10.8±0.54 mmol/L) and PaCO2 (47.8±2.54 to 23.2±0.74 mmHg) and accompanied by hyperventilation. Phe or ACh infusion did not affect arterial or venous blood pressure in the CMA group. However, the ACh infusion decreased the arterial blood pressure (ΔBP: -28.0±2.35 mm Hg [AMA] to -4.5±2.89 mmHg [control]) in the AMA group. Plasma NOx was normal after CMA but increased after AMA (25.3±0.88 to 31.3±0.54 µM). These results indicate that AMA, but not CMA, potentiated the Ach-induced decrease in blood pressure and led to an increase in plasma NOx, reinforcing the effect of pH imbalance on vascular tone and blood pressure control.

Effects of NO/cGMP inhibitors in a rat model of anaphylactoid shock

Anaphylactic shock can be defined as an acute syndrome, and it is the most severe clinical manifestation of allergic diseases. Anaphylactoid reactions are similar to anaphylactic events but differ in the pathophysiological mechanism. Nitric oxide (NO) inhibitors during anaphylaxis suggest that NO might decrease the signs and symptoms of anaphylaxis but exacerbate associated vasodilation. Therefore, blocking the effects of NO on vascular smooth muscle by inhibiting the guanylate cyclase (GC) would be a reasonable strategy. This study aimed to investigate the effects of NO/cGMP pathway inhibitors methylene blue (MB), Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and indigo carmine (IC) in shock induced by compound 48/80 (C48/80) in rats. The effect was assessed by invasive blood pressure measurement. Shock was initiated by C48/80 intravenous bolus injection 5 min before (prophylactic) or after (treatment) the administration of the inhibitors MB (3 mg/kg), L-NAME (1 mg/kg), and IC (3 mg/kg). Of the groups that received drugs as prophylaxis for shock, only the IC group did not present the final systolic blood pressure (SBP) better than the C48/80 group. Regarding shock treatment with the drugs tested, all groups had the final SBP similar to the C48/80group. Altogether, our results suggested that inhibition of GC and NO synthase in NO production pathway was not sufficient to revert hypotension or significantly improve survival.

Protective effect of N-acetylcysteine against oxygen radical-mediated coronary artery injury.

The present study investigated the protective effect of N-acetylcysteine (NAC) against oxygen radical-mediated coronary artery injury. Vascular contraction and relaxation were determined in canine coronary arteries immersed in Kreb's solution (95% O2-5% CO2), incubated or not with NAC (10 mM), and exposed to free radicals (FR) generated by xanthine oxidase (100 mU/ml) plus xanthine (0.1 mM). Rings not exposed to FR or NAC were used as controls. The arteries were contracted with 2.5 microM prostaglandin F2alpha. Subsequently, concentration-response curves for acetylcholine, calcium ionophore and sodium fluoride were obtained in the presence of 20 microM indomethacin. Concentration-response curves for bradykinin, calcium ionophore, sodium nitroprusside, and pinacidil were obtained in the presence of indomethacin plus Nomega-nitro-L-arginine (0.2 mM). The oxidative stress reduced the vascular contraction of arteries not exposed to NAC (3.93 +/- 3.42 g), compared to control (8.56 +/- 3.16 g) and to NAC group (9.07 +/- 4.0 g). Additionally, in arteries not exposed to NAC the endothelium-dependent nitric oxide (NO)-dependent relaxation promoted by acetylcholine (1 nM to 10 microM) was also reduced (maximal relaxation of 52.1 +/- 43.2%), compared to control (100%) and NAC group (97.0 +/- 4.3%), as well as the NO/cyclooxygenase-independent receptor-dependent relaxation provoked by bradykinin (1 nM to 10 microM; maximal relaxation of 20.0 +/- 21.2%), compared to control (100%) and NAC group (70.8 +/- 20.0%). The endothelium-independent relaxation elicited by sodium nitroprusside (1 nM to 1 microM) and pinacidil (1 nM to 10 microM) was not affected. In conclusion, the vascular dysfunction caused by the oxidative stress, expressed as reduction of the endothelium-dependent relaxation and of the vascular smooth muscle contraction, was prevented by NAC.

Ionic radiocontrast inhibits endothelium-dependent vasodilation of the canine renal artery in vitro: possible mechanism of renal failure following contrast medium infusion.

To determine if radiocontrast impairs vascular relaxation of the renal artery, segments (4-5 mm in length) of canine renal artery were suspended in vitro in organ chambers to measure isometric force (95% O2/5% CO2, at 37 C). Arterial segments with and without endothelium were placed at the optimal point of their length-tension relation and incubated with 10 microM indomethacin to prevent synthesis of endogenous prostanoids. The presence of nonionic radiocontrast (iohexol, Omnipaque 350, 1 ml in 25 ml control solution, 4% (v/v)) did not alter endothelium-dependent relaxation to acetylcholine in rings precontracted with both norepinephrine and prostaglandin F2alpha (N = 6). When the rings were precontracted with prostaglandin F2alpha, the presence of ionic contrast did not inhibit the relaxation of the arteries. However, in canine renal arteries contracted with norepinephrine, the presence of ionic radiocontrast (diatrizoate meglumine and diatrizoate sodium, MD-76, 1 ml in 25 ml control solution, 4% (v/v)) inhibited relaxation in response to acetylcholine, sodium nitroprusside (N = 6 in each group), and isoproterenol (N = 5; P < 0.05). Rings were relaxed less than 50% of norepinephrine contraction. Following removal of the contrast, vascular relaxation in response to the agonists returned to normal. These results indicate that ionic radiocontrast nonspecifically inhibits vasodilation (both cAMP-mediated and cGMP-mediated) of canine renal arteries contracted with norepinephrine. This reversible impairment of vasodilation could inhibit normal renal perfusion and act as a mechanism of renal failure following radiocontrast infusion. In the adopted experimental protocol the isoproterenol-induced relaxation of renal arteries precontracted with norepinephrine was more affected, suggesting a pivotal role of the cAMP system.

Pharmacological studies on internal mammary artery bypass grafts. Action of endogenous and exogenous vasodilators and vasoconstrictors.

BACKGROUND: The purpose of this experiment was four-fold: 1) to determine the effect of currently used cardiovascular drugs on internal mammary artery (IMA) vascular tone, 2) to examine IMA reactivity to autacoids and products released from aggregating platelets, 3) to compare the vascular reactivity of the right versus left IMA, and 4) to determine whether the canine IMA was an acceptable physiological model as regards its similarity to the human IMA, which is used routinely for coronary artery bypass grafting. METHODS: To study factors that modulate the tone of IMA, bypass grafts, right and left canine IMAs were studied in vitro in organ chambers (95% O(2)/5% CO(2), pH=7.4). RESULTS: Increasing concentrations (10(-9) to 10(-4M)) of the neurotransmitter acetylcholine (ACH) and the platelet-derived products adenosine diphosphate (ADP) or serotonin (5-HT) induced vasodilatation of contracted right and left IMAs. The vasodilation caused by ACH and ADP was endothelium-dependent while serotonin acted directly on the vascular smooth muscle. Histamine and bradykinin also induced IMA vasodilation, histamine via a direct action on the smooth muscle, and bradykinin through the release of nitric oxide (NO). In canine IMAs, the calcium ionophore A23187 produced endothelium-dependent vasodilation of contracted blood vessels; this vasodilation was blocked by N(G)-nitro-L-arginine (10(-4)M), a competitive inhibitor of nitric oxide synthesis from L-arginine, and by hemoglobin (10(-5)M). Dopamine, dobutamine, and papaverine induced vasodilation of the IMA regardless of the presence or absence of an intact intima, while norepinephrine induced profound IMA vasoconstriction, which was comparable to contraction to potassium ions or the constrictor peptide endothelin. CONCLUSIONS: These experiments establish a pharmacological profile of IMA and demonstrate that endogenous and exogenous compounds can significantly alter its vascular tone.

Evaluation of oxidative stress in the late postoperative stage of liver transplantation.

INTRODUCTION: Liver transplant recipients are at an increased oxidative stress risk due to pre-existing hepatic impairment, ischemia-reperfusion injury, immunosuppression, and functional graft rejection. This study compared the oxidative status of healthy control subjects, patients with liver cirrhosis on the list for transplantation, and subjects already transplanted for at least 12 months. PATIENTS AND METHODS: Sixty adult male patients, aged between 27 and 67 years, were subdivided into 3 groups: a control group (15 healthy volunteers), a cirrhosis group (15 volunteers), and a transplant group (30 volunteers). Oxidative stress was evaluated by activity of reduced glutathione, malondialdehyde, and vitamin E. RESULTS: There was a significant difference (P < .01) in the plasma concentration of reduced glutathione in the 3 groups, with the lowest values observed in the transplanted group. The malondialdehyde values differed significantly (P < .01) among the 3 groups, with the transplanted group again having the lowest concentrations. The lowest concentrations of vitamin E were observed in patients with cirrhosis compared with control subjects, and there was a significant correlation (P < .05) among the 3 groups. No correlations were found between reduced glutathione and vitamin E or between vitamin E and malondialdehyde. However, there were strong correlations between plasma malondialdehyde and reduced glutathione in the 3 groups: control group, r = 0.9972 and P < .0001; cirrhotic group, r = 0.9765 and P < .0001; and transplanted group, r = 0.8981 and P < .0001. CONCLUSIONS: In the late postoperative stage of liver transplantation, oxidative stress persists but in attenuated form.

Should preconditioning hyperbaric oxygenation protect the liver against ischemia-reperfusion injury? An experimental study in a rat model.

OBJECTIVES: We designed studies to test the hypotheses that hyperbaric oxygen (HBO) therapy should protect liver against subsequent ischemia/reperfusion (I/R) injury are scarce and controversial. The purpose of this study was to clarify some questions about the association of HBO with the processes of liver I/R. METHODS: We divided Wistar rats into 5 groups: (1) SHAM operation, (2) I/R, rats submitted to total pedicle ischemia for 30 minutes followed by 5 minutes of reperfusion; (3) HBO60I/R and (4) HBO120I/R, rats respectively submitted to 60 and 120 minutes of HBO therapy at 2 absolute atmospheres and immediately after submitted to the experimental protocol of I/R; (5) HBO120, rats submitted to 120 minutes of HBO therapy at 2 absolute atmospheres and then immediately after humanely killed. The experimental protocol included (1) serum levels of aspartate and alanine aminotransferase; (2) mitochondrial function; (3) tissue malondialdehyde (MDA); and (4) plasma nitrite/nitrate. Data were analyzed using the Mann-Whitney test and were considered significant P < 5%. RESULTS: The processes of liver ischemia/reperfusion caused tissue injury with hepatic mitochondrial functional impairment. A single exposure to 120 minutes of HBO caused an increase of tissue MDA. The time of HBO exposure as preconditioning before hepatic I/R is critical in the prevalence of beneficial or deleterious effects. Sixty minutes of hyperoxic preconditioning before liver I/R presents systemic benefits, but no significant tissue preservation. One hundred twenty minutes of hyperoxic preconditioning tissue liver benefits predominate compared with systemic benefits. CONCLUSIONS: The HBO preconditioning therapeutic benefits to liver I/R injury are time dependent, suggesting a therapeutic window that needs to be clearly defined in future studies.

Acute but not chronic metabolic acidosis potentiates the acetylcholine-induced reduction in blood pressure: an endothelium-dependent effect

Metabolic acidosis has profound effects on vascular tone. This study investigated the in vivo effects of acute metabolic acidosis (AMA) and chronic metabolic acidosis (CMA) on hemodynamic parameters and endothelial function. CMA was induced by ad libitum intake of 1% NH4Cl for 7 days, and AMA was induced by a 3-h infusion of 6 M NH4Cl (1 mL/kg, diluted 1:10). Phenylephrine (Phe) and acetylcholine (Ach) dose-response curves were performed by venous infusion with simultaneous venous and arterial blood pressure monitoring. Plasma nitrite/nitrate (NOx) was measured by chemiluminescence. The CMA group had a blood pH of 7.15±0.03, which was associated with reduced bicarbonate (13.8±0.98 mmol/L) and no change in the partial pressure of arterial carbon dioxide (PaCO2). The AMA group had a pH of 7.20±0.01, which was associated with decreases in bicarbonate (10.8±0.54 mmol/L) and PaCO2 (47.8±2.54 to 23.2±0.74 mmHg) and accompanied by hyperventilation. Phe or ACh infusion did not affect arterial or venous blood pressure in the CMA group. However, the ACh infusion decreased the arterial blood pressure (ΔBP: -28.0±2.35 mm Hg [AMA] to -4.5±2.89 mmHg [control]) in the AMA group. Plasma NOx was normal after CMA but increased after AMA (25.3±0.88 to 31.3±0.54 μM). These results indicate that AMA, but not CMA, potentiated the Ach-induced decrease in blood pressure and led to an increase in plasma NOx, reinforcing the effect of pH imbalance on vascular tone and blood pressure control.