Trisulfate disaccharide decreases calcium overload and protects liver injury secondary to liver ischemia/reperfusion

Background Ischemia and reperfusion (I/R) causes tissue damage and intracellular calcium levels are a factor of cell death. Sodium calcium exchanger (NCX) regulates calcium extrusion and Trisulfated Disaccharide (TD) acts on NCX decreasing intracellular calcium through the inhibition of the exchange inhibitory peptide (XIP). Objectives The aims of this research are to evaluate TD effects in liver injury secondary to I/R in animals and in vitro action on cytosolic calcium of hepatocytes cultures under calcium overload. Methods Wistar rats submitted to partial liver ischemia were divided in groups: Control: (n = 10): surgical manipulation with no liver ischemia; Saline: (n = 15): rats receiving IV saline before reperfusion; and TD: (n = 15): rats receiving IV TD before reperfusion. Four hours after reperfusion, serum levels of AST, ALT, TNF-α, IL-6, and IL-10 were measured. Liver tissue samples were collected for mitochondrial function and malondialdehyde (MDA) content. Pulmonary vascular permeability and histologic parameters of liver were determined. TD effect on cytosolic calcium was evaluated in BRL3A hepatic rat cell cultures stimulated by thapsigargin pre and after treatment with TD. Results AST, ALT, cytokines, liver MDA, mitochondrial dysfunction and hepatic histologic injury scores were less in TD group when compared to Saline Group (p<0.05) with no differences in pulmonary vascular permeability. In culture cells, TD diminished the intracellular calcium raise and prevented the calcium increase pre and after treatment with thapsigargin, respectively. Conclusion TD decreases liver cell damage, preserves mitochondrial function and increases hepatic tolerance to I/R injury by calcium extrusion in Ca2+ overload situations

Role of acetylcholine in electrical stimulation-induced arrhythmia in rat isolated atria

In this study, we used the spontaneously beating, isolated rat right atrium as an in vitro model to study arrhythmogenic effects of electrical stimulation. A tetrapolar platinum electrode was used for stimulation and recording of atrial electrical activity at 36.5 degrees C (spontaneous rate, 4.9 +/- 0.3 Hz). A flutter-like pattern of arrhythmia was reproducibly induced by application of stimulus trains (250 pulses, 66.7 Hz), Arrhythmia was characterized by regular and very short cycle length (40-70 ms), each episode lasting from 3 s to >5 min. In control conditions, application of one to five pulse trains was sufficient to induce arrhythmia. However, atropine (but not propranolol) completely blocked arrhythmia induction (10-15 consecutive trains were ineffective). The ability of electrical stimulation to evoke arrhythmia was restored after atropine washout. A milder stimulation protocol(30 pulses, 50 Hz), which was unable to evoke arrhythmia in control conditions, was fully effective in the presence of 1 mu M acetylcholine (ACh). Furthermore, a similar flutter-like pattern could be induced in isolated left atria in the presence of ACh, Our results point out an arrhythmogenic effect of neurally released ACh in the isolated right atrium on atrial electrical stimulation.34447547