Effect of Nitric Oxide Synthesis Blockade on the Morphology of Langerhans Islets in August and Wistar Rats with Acute Alloxan Diabetes.

Alloxan diabetes was modeled in August rats with high activity of the NO system and in Wistar rats, and the effects of NO system blockade (by a course treatment with L-NNA) on Langerhans islet ß cells were studied in 15 days. The toxic effects of diabetes on the rat ß cells and islets were similar: the content of active ß cells in the islets decreased to 15-20%, the number of islets to 24-29% of control. A course of L-NNA reduced the ß cell and islet death, in August cells greater than in Wistar: the number of islets in August rats was restored to 81%, in Wistar rats to 60% of initial level; the activity of ß cells remained at the control level in the former and 2-fold lower than in the control in the latter. It seems that a less pronounced protective effect of L-NNA in Wistar rats was explained by excessive reduction of NO level essential for ß cell regeneration.

[Antiarrhythmic effect of oligonucleotides accompanied by activation of HSP70 protein in the heart of rats].

UNLABELLED: The mechanisms of the protective effect of oligonucleotides (OGN) during pathological processes are poorlyunderstood. The goal of this work was to study the effect of OGN on arrhythmias induced by myocardial ischemia and reperfusion, and the HSP70 level in the heart. As a source of OGN was used the drug "Derinat" ("Technomedservis", Russia). In male Wistar rats were pre-treated the drug for 7 days (i/m, 7.5 mg/kg).The intensity of the arrhythmias was assessed by ECG during 10 min occlusion of the left coronary artery and subsequent 5 min of reperfusion. Protein HSP70 determined in the left ventricle of the heart by Western-blot analysis. During ischemia, this drug reduced duration of extrasystolia by 13 times and the incidence of ventricular tachycardia by 1.5 times. During reperfusion the drug reduced the incidence of ventricular fibrillation, a more than 2-fold, as compared with the control (respectively 23% vs 56%) and by 5 times its duration (8,4 ± 2,3 48,1 ± sec vs 18 7 sec). "Derinat" increased the HSP70 level in the heart by 65% compared with control. CONCLUSION: These data support the fact that the activation of HSP70 synthesis, induced by OGN is one of the mechanisms that increases the heart resistance to the ischemic and reperfusion damages.

[Effect of adaptation to hypoxia on expression of NO synthase isoforms in rat myocardium].

Previously we have shown that adaptation to hypoxia (AH) is cardio- and vasoprotective in myocardial ischemic and reperfusion injury and this protection is associated with restriction of nitrosative stress. The present study was focused on further elucidation of NO-dependent mechanisms of AH by identifying specific NO synthases (NOS) that could play the major role in AH protection. AH was performed in a normobaric hypoxic chamber by breathing hypoxic gas mixture (9.5-10% O2) for 5-10 min with intervening 4 min normoxia (5-8 cycles daily for 21 days). Expression of neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) protein was measured in the left ventricular myocardium using Western blot analysis with respective antibodies. AH educed iNOS protein expression by 71% (p < 0.05) whereas eNOS protein expression tended to be reduced by 41% compared to control (p < 0.05). nNOS protein expression remained unchanged after AH. Selective iNOS inhibition can mimic the AH-induced protection. Therefore protective effects of AH could be at least partially due to restriction of iNOS and, probably, eNOS expression.

[Effect of the alloxane diabetes on the cardio-vascular system function and lipid peroxidation in rats of different genetic strains].

We have previously shown that the innate increased activity of the NO- system, typical for the August rats, increases vulnerability to alloxane diabetes (ALD). The purpose of this study was to investigate the effect of ALD on the cardiovascular system and lipid peroxidation in rats with different activity of NO-system. The August rats and Wistar rats treated with alloxan (125 mg/kg, s/c, once) were studied 3.5 months after. In August-ALD the double production significantly decreased to a greater extent (by 35%) than in Wistar-ALD (by 17%) compared with the control. As in August-ALD and in Wistar-ALD was observed the similar fall of the relaxation (-dp/dt) of the left ventricle (by 45-49%), but not the contraction rate (+dp/dt). LPO activation in the heart and liver, as well as NO-system (level of nitrates and nitrites in the blood plasma) in August rats were more pronounced than in Wistar rats. The hsp32 level in August rats fell significantly more (by 93% ) than in Wistar rats (by 61%). Pathological changes in the microvasculature of the mesostenium were identical in compared rats. Thus, more pronounced cardiac dysfunction in August-ALD, compared with Wistar-ALD, associated with greater activation of lipid peroxidation and NO-system.

Role of nitric oxide in the pathogenesis of alloxan diabetes.

We studied the effects of N(w)-nitro-L-arginine (L-NNA), a nonselective inhibitor of NO synthases, on the severity of type 1 diabetes mellitus induced by subcutaneous injection of 130 mg/kg alloxan in August rats with high activity of NO system and in Wistar rats. Five days after alloxan injection, hyperglycemia levels after overnight fasting in August and Wistar rats were 27.1±3.7 and 22.0±1.1 mmol/liter, respectively (p<0.03). The mortality over 15 days after alloxan injection in August rats was higher than in Wistar rats (36 and 26%, respectively). L-NNA normalized glucose levels in diabetics of both groups. It completely prevented mortality in August and reduced it to 13% in Wistar rats. Body weight loss and polydipsia after L-NNA injection were also less pronounced in August rats. Plasma nitrite/nitrate concentrations in August rats were 32% higher than in Wistar rats, both in intact and diabetic rats. These data attest to an important role of NO in the pathogenesis of alloxan diabetes.

[Effect of NO-synthesis blockade on the free-radical processes in rats of different genetic strains with acute alloxan diabetes].

Previously, we have shown that nitric oxide (NO) plays an important role in the pathogenesis of alloxan diabetes (ALD). In this study in August rats, with the congenital increased activity of NO, and in Wistar rats was induced ALD (130 mg/kg, p/c) and 15 days after were examined the effects of the NO-blockade synthesis, induced by administration of Nω-nitro-L-arginine (L-NNA) cour- se on the activity of lipid peroxidation (LP), HIF-1α level, the degree of NO-system activation. The activation of iNOS, HIF-1a expression and 3-nitrotyrosine accumulation in liver were more pronounced in August-ALD rats than in Wistar-ALD rats. The level of TBA-active products in the heart and liver was increased in both diabetic groups only in the first 3 days ofALD and then this indicator of LP sharply was decreased as compared with the control. This effect was pronounced more in August rats. The inhibition of NO overproduction reduced significantly the severity of ALD and prevented the activation of LP, iNOS and HIF-1a. Thus, these data suggest, that NO plays an important role in the pathogenesis of ALD and in the regulation of oxygen homeostasis.

[Vasoprotective effect of adaptation to hypoxia in myocardial ischemia and reperfusion injury].

Adaptation to hypoxia is known to be cardioprotective in ischemic and reperfusion (IR) injury of the myocardium. This study was focused on investigating a possibility for prevention of endothelial dysfunction in IR injury of the rat heart using adaptation to intermittent hypoxia, which was performed in a cyclic mode (5-10 min of hypoxia interspersed with 4 min of normoxia, 5-8 cycles daily) for 21 days. Endothelial function of coronary blood vessels was evaluated after the in vitro IR of isolated heart (15 min of ischemia and 10 min of reperfusion) by the increment of coronary flow rate in response to acetylcholine. Endothelium-dependent relaxation of isolated rat aorta was evaluated after the IR myocardial injury in situ (30 min of ischemia and 60 min of reperfusion) by a relaxation response of noradrenaline-precontracted vessel rings to acetylcholine. The following major results were obtained in this study: 1) IR myocardial injury induced endothelial dysfunction of coronary blood vessels and the aorta, a non-coronary blood vessel, remote from the IR injury area; and 2) adaptation to hypoxia prevented the endothelial dysfunction of both coronary and non-coronary blood vessels associated with the IR injury. Therefore, adaptation to hypoxia is not only cardioprotective but also vasoprotective in myocardial IR injury.

[Role of restricted nitric oxide overproduction in the cardioprotective effect of adaptation to intermittent hypoxia].

Adaptation to intermittent normobaric hypoxia is cardioprotective and can stimulate nitric oxide (NO) synthesis. However the role of nitric oxide (NO) in prevention of ischemia-reperfusion (IR) injury of myocardium is controversial. This study was focused on evaluating the effect of adaptation to hypoxia and IR on NO production and development of nitrative stress in the myocardium. Adaptation to hypoxia tended to increase NO production, which was determined by the total level of plasma nitrite and nitrate, and prevented IR-induced NO overproduction. The IR-induced NO overproduction was associated with significant 3-nitrotyrosine (3-NT) accumulation in the left ventricle but not in septum or aorta. In hypoxia-adapted rats, 3-NT after IR was similar to that of control rats without IR. IHC induced marked accumulation of HIF-1alpha in the left ventricle. We suggest that HIF-1alpha contributes to NO-synthase expression during adaptation to hypoxia and thereby facilitates the increase in NO production. NO, in turn, may subsequently prevent NO overproduction during IR by a negative feedback mechanism.

Effect of acute alloxan diabetes on ischemic and reperfusion arrhythmias in rats with different activity of nitric oxide system.

Similar degree of glycemia (28-31 mmol/liter) and similar mortality (37-42%) were revealed in August rats exhibiting enhanced activity of NO system and in Wistar rats 3 weeks after alloxan treatment. Under conditions of myocardial ischemia caused by 10-min coronary artery ligation, the intensity of arrhythmias did not differ from the control in Wistar rats with diabetes mellitus and increased in August rats. Under conditions of reperfusion, diabetes produced an antiarrhythmic effect in Wistar rats and did not affect arrhythmia in August rats. Plasma concentrations of nitrates and nitrites in Wistar and August rats increased by 82 and 143%, respectively, compared to the control. The level of hemoxygenase-1 (hsp32) in the myocardium remained unchanged in Wistar rats and decreased by 26% in August rats. Thus, the absence of antiarrhythmic effect of acute diabetes in August rats is probably related to elevated NO content and reduced antioxidant activity.

[Particularities of adrenergic regulation and the function of cardiovascular system at remote periods after myocardial infarction in rats of different strains].

UNLABELLED: Heart function was studied in the August rats with innate raised sympathetic-adrenal system and in the Wistar rats through the period of 3 month after myocardial infarction. The sizes of the postinfarction scars were similar in the rats under comparison (56-62%) but end-diastolic pressure in Wistar rats and in August rats was 18.7 +/- 2.2 mm Hg and 11.8 +/- 0.7 mm Hg. Under the maximum isometric load induced by the aorta coarctation, the work efficiency of the heart in the August rats was greater than in the Wistar rats. During the postinfarction period, plasma catecholamine (CA) in August rats was higher than in Wistar rats. In the adrenal glands, the CA contents in August rats increased and in Wistar rats decreased. The activity of CA resynthes in the adrenal glands and in the hypothalamus in August rats did not change and in Wistar rats increased. The blood contents of nitrate and nitrite and hemine oxygenase-1 level in the myocardium of August rats were increased in contrast to Wistar rats. THE CONCLUSION: the higher viability of the myocardium in August rats with long existing postinfarction cardiasclerosis is to a considerable extent associated with lowered activation of the sympathetic-adrenal system under more expressing activation of NO-system and antioxidant protection.

Delta sleep-inducing peptide and Deltaran: potential approaches to antistress protection.

The aims of the present work were to perform a comparative study of the effects of delta sleep-inducing peptide and Deltaran on neurons in emotiogenic brain structures and to address the question of whether it is possible to prevent or decrease the negative influences of stress loads on the severity of subsequent cerebral ischemia in rats, using glycine with delta sleep-inducing peptide combined in the neuroprotective formulation Deltaran. The results showed that Deltaran and delta sleep-inducing peptide had largely the same actions on the nature of spike activity of neurons in the dorsal hippocampus, paraventricular nucleus of the hypothalamus, and ventral anterior nuclei of the thalamus, evoking activation of some of the neurons in these brain structures. The dorsal hippocampus was dominated by activation of spike activity in response to administration of delta sleep-inducing peptide; Deltaran produced activation mainly in the paraventricular nuclei of the hypothalamus. In all animals given Deltaran, the index of brain blood supply was significantly greater than in animals not given Deltaran. The survival rate of cerebral ischemia was 100% in animals given Deltaran. Death occurred in 38% of animals not given Deltaran.

[Delta-sleep inducing peptide and the drug deltaran: possible approaches to antistress protection].

An aim of the present study was a comparative investigation of a delta-sleep inducing peptide and the drug deltaran on the neural activity of the brain structures involved in emotional processing. Another goal was to analyze the possibility to prevent negative effects of emotional stress on brain ischemia using, along with deltaran, glycine and a delta-sleep inducing peptide. Deltaran and the delta-sleep inducing peptide exert in general similar effect on the burst activity of neurons in the dorsal hippocampus, hypothalamic paraventricular nucleus and ventral anterior thalamic nucleus, inducing amplification of the majority of recorded units. The activation of neuronal activity was seen mostly after the delta-sleep inducing peptide microiontophoresis in the dorsal hippocampus and after the deltaran application in the hypothalamic paraventricular nuclei. The index characterizing blood supply was significantly higher in all rats receiving deltaran as compared to the controls. Animals receiving deltaran survived experimental brain ischemia in 100% cases versus 38% in those not exposed to this drug.