The aim of the present study was to investigate the endothelial function in human mesenteric arteries with specific reference to defining the role of endothelium-derived nitric oxide (EDNO) and the endothelium-derived hyperpolarizing factor (EDHF). Isolated segments of small human mesenteric arteries (225-450 μm inner diameter) were mounted in organ baths for recording isometric tension. In arteries precontracted with U46619 (thromboxane A2 analogue, 10-7 M), endothelium-dependent relaxations were induced in a concentration-dependent manner by substance P and histamine. In normal Krebs solution the relaxations to substance P (10-9 M) and histamine (10-7 M) were not significantly affected by preincubation with Nω-nitro-L-arginine (L-NNA, 10-4 M) or indomethacin (10-5 M). When the preparations were exposed to a solution containing 60 mM KCl, stable contractions were induced, but relaxations could still be induced by substance P and histamine. When the arteries were further preincubated with L-NNA, the relaxations were almost abolished. A combination of apamin (3 x 10-7 M) and charybdotoxin (10-9 M) almost abolished relaxations in normal Krebs solution. It is concluded that isolated human mesenteric arteries respond to substance P and histamine with relaxations that are endothelium-dependent. Synthesis of both EDNO and EDHF seem important for these relaxations, whereas prostaglandins seem to be of minor importance.
In the present study, we investigated whether erythropoietin (Epo) has a protective effect against cytotoxicity induced by interferon-gamma (IFN-
γ) and lipopolysaccharide (LPS) in primary rat oligodendrocyte cultures. The possible modulatory effect of erythropoietin on inducible nitric oxide synthase (iNOS) mRNA expression and nitrite production were also analyzed. Erythropoietin exerted a significant protective effect against IFN-γ and LPS-induced oligodendrocyte injury as determined by lactate dehydrogenase assay. Treatment with erythropoietin inhibited the expression of iNOS mRNA and nitrite production resulting from proinflammatory stimulation by IFN-γ and LPS. These results suggest that erythropoietin has protective effects against inflammatory oligodendrocyte injury in vitro and may play a protective role in neurological disorders characterized by oligodendrocyte death, such as multiple sclerosis.
Though two isoforms of nitric oxide synthase, iNOS and eNOS, were reported in adipocytes, the role of NO in adipose tissue is still ambiguous. The aims of the present study were 1) to follow the effect of bacterial lipopolysaccharide (LPS), on 24 h-lipolysis in rat epididymal adipocyte culture in relation to iNOS stimulation; 2) to compare LPS-induced NO effects with exogenously NO, delivered as S-nitroso-N-acetylpenicillamine (SNAP), and 3) to examine the possible role of NO signaling agonist in lipolysis mediated by the -adrenoreceptor agonist. Lipolysis was measured by glycerol and free fatty acid (FFA) production. The medium nitrite levels were used for the indirect estimation of NOS expression. Adipocyte mitochondrial function was assessed by the MTT test. LPS produced a concentration-dependent increase of NO with a decrease of viability at the highest dose. However, LPS did not affect lipolysis. SNAP did not exhibit significant changes in glycerol, FFA or MTT. BRL-37344 and db-cAMP significantly increased nitrite, glycerol and FFA levels. There was a positive correlation between glycerol release and nitrite production. Moreover,
BRL-37344 significantly reduced mitochondrial functions. The pretreatment with bupranolol, -antagonist, restored all parameters affected by BRL-37344. These results support a concept that NO fulfils multifaceted role of stimulating lipolysis under physiological conditions (-agonistic effect) and modulating the same processes during inflammatory (LPS) processes.
We reported previously that the nitric oxide synthesis inhibitor Nv-nitro-L-arginine methyl ester (L-NAME) decreases cardiac output. Several studies have shown that inhibition of nitric oxide synthesis decreases the heart rate. In the present study, we investigated the effect of a single bolus administration of L-NAME on blood pressure and heart rate monitored for one hour in anesthetized rats and the influence of vagotomy and b1-receptor blocker metoprolol on the L-NAME induced bradycardia. After L-NAME treatment, the blood pressure rose immediately after the injection of the drug (peak response in the third minute: +24 %, p<0.001) and fell to the control level in the 20th minute. The heart rate decreased immediately after L-NAME administration, the lowest value being reached in the 10th minute (-14 %, p<0.001). However, bradycardia was sustained even after the blood pressure had returned to the control level. Bilateral vagotomy failed to influence the negative chronotropic effect of L-NAME, but bradycardia was completely abolished by metoprolol pretreatment. We concluded that the bradycardia evoked by L-NAME is mainly due to the withdrawal of sympathetic tone upon the heart rate. However, the cause of sustained bradycardia after normalization of blood pressure cannot be elucidated., J. Vág, C. Hably, J. Bartha., and Obsahuje bibliografii
Using histochemical analysis (NADPH-diaphorase) we have investigated the influence of intraperitoneal administration of kainic acid (KA), hypoxia and combination of both these factors on neurons of the hippocampus and on the primary auditory cortex (PAC) in male rats of the Wistar strain. Kainic acid was administered to 18-day-old animals, which were exposed to long-lasting repeated hypoxia from the 2nd till the 17th day of age in a hypobaric chamber (for 8 hours a day). At the age of 1 year, the animals were transcardially perfused with 4 % paraformaldehyde under deep thiopental anesthesia. Cryostate sections were stained to identify NADP
H-diaphorase positive neurons that were then quantified in CA1 and CA3 areas of the hippocampus, in the dentate gyrus and in the PAC. Both, hypoxia and KA lowered the number of NADPH-diaphorase positive neurons in the hilus, dorsal and ventral blades of the dentate gyrus, CA1 and CA3 areas of the hippocampus. On the contrary, KA given to the hypoxic animals increased the number of NADPH-diaphorase positive neurons in the dorsal blade of the dentate gyrus and PAC.
Microcirculatory disturbances are important early pathophysiological events in various organs during acute pancreatitis (AP). The aim of the study was to investigate an influence of L-arginine (nitric oxide substrate) and NG-nitro-L-arginine (L-NNA, nitric oxide synthase inhibitor) on organ microcirculation in experimental acute pancreatitis induced by four consecutive intraperitoneal cerulein injections (15 μg/kg/h). The microcirculation of pancreas, liver, kidney, stomach, colon and skeletal muscle was measured by laser Doppler flowmeter. Serum interleukin 6 and hematocrit levels were analyzed. AP resulted in a significant drop of microperfusion in all examined organ. L-arginine administration
(2x100 mg/kg) improved the microcirculation in the pancreas, liver, kidney, colon and skeletal muscle, and lowered hematocrit levels. L-NNA treatment (2x25 mg/kg) caused aggravation of edematous AP to the necrotizing situation, and increased IL-6 and hematocrit levels. A further reduction of blood perfusion was noted in the stomach only. It is concluded that L-arginine administration has a positive influence on organ microcirculatory disturbances accompanying experimental cerulein-induced AP. NO inhibition aggravates the course of pancreatitis.
It was previously shown that 4 hours´ lasting inhibition of nitric oxide synthesis by administration of an L-arginine analogue, the NG-nitro-L-arginine methyl ester (L-NAME) changed the affinity of the Na-binding site of Na,K-ATPase thus resulting in elevation of enzyme activity especially at higher concentrations of sodium. Using the same experimental model, we focused our attention in the present study to the question of binding of ATP to the enzyme molecule in the left ventricle (LV), ventricular septum (S) and the right ventricle (RV) of the dog heart. Activation of the enzyme by increasing concentrations of ATP revealed a significant increase of the Vmax only in septum (by 38 %). The KM increased significantly in septum (by 40 %) and in left ventricle (by 56 %) indicating an altered sensitivity of the ATP-binding site of Na,K-ATPase in the hearts of NO-deficient animals. The alterations of Na,K-ATPase in its ability to bind and hydrolyze ATP are localized to the tissue surrounding the cavity of the left ventricle., N. Vrbjar, M. Strnisková, O. Pecháňová, M. Gerová., and Obsahuje bibliografii
The impact on blood pressure of two vasodilating mechanisms, underlied by vascular smooth muscle hyperpolarization, was studied and compared to that induced by nitric oxide (NO) mechanism. Systemic blood pressure, after inhibitory intervention in arachidonic acid metabolism (cytochrome P-450 inhibition by miconazole 0.5 mg/100 g b.w.), one of the hyperpolarizing pathways, did not change. After the inhibition of the action voltage-dependent K+ channels operator (by 4-aminopyridine 0.1 mg/100 g b.w.)
, the other hyperpolarizing pathway, blood pressure declined slightly (from 132.3±3.2 mm Hg to 116.5±5.0 mm Hg, P<0.05). Inhibition of nitric oxide production (L-NAME 5 mg/100 g b.w.) increased blood pressure considerably (123.5±2.7 mm Hg to 155.4±3.1 mm Hg, P<0.001). After inhibition of the hyperpolarizing pathway by miconazole, hypotension induced by acetylcholine (Ach, 10 μg) represented 63.0±1.9 mm Hg vs control value 78.6±5.2 mm Hg (P<0.001), by bradykinin (BK) (100 μg) 59.4±3.9 mm Hg vs control value 71.2±6.1 mm Hg (P<0.05). After inhibition of the hyperpolarizing pathway by 4-aminopyridine, hypotension induced by ACh (10 μg) achieved 64.6±2.5 mm Hg vs control value 78.4±2.8 mm Hg (P<0.001) and that induced by BK (100 μg)
56.6±5.3 mm Hg vs control value 72.3±2.5 mm Hg (P<0.001). ACh or BK hypotension after the inhibition of the above hyperpolarizing pathways was significantly attenuated. On the contrary, after NO-synthase inhibition the hypotension to ACh was significantly enhanced. Blood pressure decrease after ACh (10 μg) hypotension was 91.8±4.1 mm Hg vs control value 79.3±3.3 mm Hg (P<0.01), and after BK (100 μg) it was 78.4±7.1 mm Hg vs control value 68.3±5.2 mm Hg. A different basal BP response, but equally attenuated hypotension to Ach and BK, was detected after the inhibition of two selected hyperpolarizing pathways. In cotrast, the inhibition of NO production elicited an increase in systemic BP and augmentation of ACh and BK hypotension. The effectiveness of further hyperpolarizing mechanisms in relation to systemic BP regulation and nitric oxide level remains open.
The effects of nitroglycerine (NTG) are mediated by liberated nitric oxide (NO) after NTG enzymatic bio-transformation in cells. The aim of this study was to evaluate some products of NTG bio-transformation and their consequences on the redox status of rat erythrocytes and reticulocytes, considering the absence and presence of functional mitochondria in these cells, respectively. Rat erythrocyte and reticulocyte-rich red blood cell (RBC) suspensions were aerobically incubated (2 h, 37 0C) without (control) or in the presence of different concentrations of NTG (0.1, 0.25, 0.5, 1.0 and 1.5 mM). In rat erythrocytes, NTG did not elevate the concentrations of any reactive nitrogen species (RNS). However, NTG robustly increased concentration of methemoglobin (MetHb), suggesting that NTG bio-transformation was primarily connected with hemoglobin (Hb). NTG-induced MetHb formation was followed by the induction of lipid peroxidation. In rat reticulocytes, NTG caused an increase in the levels of nitrite, peroxinitrite, hydrogen peroxide, MetHb and lipid peroxide levels, but it decreased the level of the superoxide anion radical. Millimolar concentrations of NTG caused oxidative damage of both erythrocytes and reticulocytes. These data indicate that two pathways of NTG bio-transformation exist in reticulocytes: one generating RNS and the other connected with Hb (as in erythrocytes). In conclusion, NTG bio-transformation is different in erythrocytes and reticulocytes due to the presence of mitochondria in the latter.