Protective Role of Vitamin E. J Clin Med Res • 2012;4(3):190-196 Figure 2. Electron micrographs from cardiac atria of amiodarone-treated rats. A. A semithin section showing abnormal pattern of striations (stars), disrupted intercalated discs (arrow) and abnormal mitochondrial arrangements (double arrows). B. Dissociation of myofibrils (stars) with irregularities and destruction of myofibrils and intercalated disc (arrow) (Bar = 200 nm). C. Dissociation of myo- fibrils (stars) with irregularities of the sarcomere and lesser concentration of ANF granules (An) with disrupted nuclear (N) chromatin contents (Bar = 1 µm). D. Swollen mitochondria (M) with loss of its cristae in some and loss of its pattern in others. Empty spaces in between myofibrils (m) and fibres (F) were noted in the intercellular space (Bar = 1 µm). (x: 1000). were performed in agreement with the Principles of Labo- ratory Animal Care, advocated by the National Society of Medical Research and the Guide for the Care and Use of Laboratory Animals and published by the National Research Council [23]. Experimental procedure The rats were divided randomly into 3 groups of 6 rats each. All drugs were given in a final volume of 2 mL/day, orally using intra-gavage stainless steel needle for 2 weeks. The groups of rats were classified as follows: (a) the control group received vegetable oil; (b) group 2 received amioda- rone (54 mg/kg) alone; and (c) group 3 received both amio- darone (54 mg/kg) and alpha tocopherol acetate (50 mg/kg). Preparation of atrial tissue for electron microscopy After the treatment period, small pieces of the harvested atrial cardiac muscle were fixed in 2.5% glutaraldehyde for 24 hours and washed by phosphate buffer (0.1 M, pH 7.4). Post fixation was made in 1% osmium tetroxide buffered to pH 7.4 with 0.1 M phosphate buffer at 4 oC for 1 - 2 hours. Specimens were washed again in phosphate buffer to remove excess fixative and dehydrated through ascending concentra- tions of ethanol. The specimens were then cleared in pro- pylene oxide and embedded in araldite. Polymerisation was obtained by placing the capsules at 60 oC. Ultra-thin sections (100 nm) were prepared using an ultra microtome and were placed on uncoated copper grids. Following double staining with uranyl acetate and lead citrate, sections were examined and photographed using a JEOL transmission electron mi- croscope [24]. The specimens were prepared and read by a blinded histopathologist who was unaware of the different treatment groups. Results Group I (Control group) Electron microscopic examination of the sections from the rat atria of the control group showed normal architecture. The mitochondria were packed together between myofibrils with some beneath the sarcolemma and some around the nu- cleus with visible intercalated discs (Fig. 1A). The striation pattern, with its typical alteration and dense mitochondria rich in cristae, was clearly visible in cardiac muscle (Fig. 1B, 192 Articles © The authors | Journal compilation © J Clin Med Res and Elmer Press™ | www.jocmr.org