Magnesium plays an essential role in many fundamental biological reactions, as it is involved in more than 300 metabolic reactions. Deficiency of magnesium may result in many disorders, including cardiac arrhythmias. As intravenous magnesium has a high therapeutic to toxic ratio and a minimal negative inotropic effect, it has long been used in treatment and prevention of cardiac arrhythmias. Several studies have shown the beneficial effect of intravenous infusion of Mg during an attack of supraventricular tachycardia, indicating that the effectiveness of magnesium depends on the type of tachycardia. Magnesium has also an advantageous effect in the case of atrial fibrillation, considered a criterion of the effectiveness of atrial fibrillation acute treatment at the ventricular rate ? 100 min –1 . As intravenous magnesium seems to be useful in prevention and treatment of various cardiac arrhythmias, it is a common component of a complex antiarrhythmic therapy.
Cessation of blood flow in tissues leads to depletion of energetic resources of cells, disturbances in the activity of enzymes of the oxidative chain and electrolyte disorders, as well as to the production of reactive oxygen species. A great deal of attention has been paid to those problems since they are responsible for most of the complications in the ischemia-reperfusion (I/R) syndrome. Understanding the antioxidative mechanisms involved in I/R syndrome provides us with the potential to correct at least some of the resulting disturbances. One of the potentially beneficial factors is insulin. This observation directed our attention to the insulin-like factors, kinins (especially bradykinin), the activation of which was detected in I/R syndrome. The effect of bradykinin is modified by concurrent administration of the specific antagonists of bradykinin receptors, B1 and B2. The aim of the current study was to assess the role of bradykinin. In the study, the employed agents included the angiotensin converting enzyme inhibitor, which prevents the degradation of endogenous kinins, and blockers of bradykinin receptors, which abolish the influence of kinins. We observed that after 4 hours of ischemia followed by reperfusion, levels of free radicals in tissues as well as levels of peroxides in plasma increased significantly. Administration of bradykinin, captopril or enalapril resulted in the decline of these free radical levels. The application of B2 receptor antagonist decreased the beneficial influence of bradykinin, whereas B1 receptor antagonist revealed no significant effect. Activities of antioxidative enzymes (superoxide dismutase, catalase, and glutathione peroxidase) were measured. After 4 hours of ischemia and consecutive steps of reperfusion, a statistically significant increase in their activities was observed when bradykinin or ACE inhibitors were administered. Application of B2 receptor blockers reduced the effect of bradykinin, whereas the effect of B1 receptor antagonists was minute.
Acute ischemia and the subsequent reperfusion caused by temporary closure of blood flow in the main arteries, which activate generalized inflammatory response, lead to endothelial injury. The aim of the study was to examine the injury of tissues in the ischemia reperfusion syndrome. Additionally, we tried to estimate the role of B1 and B2 bradykinin-receptor antagonists. In our study we histologically assessed specimens of lungs, kidney, liver, small and large intestine and skeletal muscle from the thigh. We compared the samples obtained from the groups of animals that were exposed to 4 hours of complete ischemia and 120 minutes of reperfusion. We divided animals into 4 groups. Rats in the first group were the control group, animals from the second received bradykinin. In the third and fourth group respectively bradykinin along with B2 and B1 bradykinin-receptor antagonist were administered. The results of microscopic examination revealed that bradykinin exerts a protective effect on the function and structure of distant organs as well as the skeletal muscle which was subjected to ischemia and reperfusion. The most visible effects of bradykinin were found in the samples of the lung, skeletal muscle, and the large and small intestines. Administration of bradykinin receptor antagonists, especially B2 receptor blocker, reduces the advantageous effects of bradykinin. The conclusion of our study is that administration of bradykinin may be beneficial in diseases accompanied by limb ischemia where tissue blood flow and oxygen metabolism are dependent upon kinin release, which in turn will condition tissue repair.
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