Histological and scanning electron microscopic study of the effect of cigarette smoke on the heart of male albino rats

Environmental tobacco smoke has been shown to cause heart diseases among non-smokers. Twenty one adult male albino rats were used to investigate the effect of cigarette smoke on the heart and to evaluate the possibility of recovery. Rats were divided into 3 equal groups. Rats of group I were considered as control Rats of group II were exposed to cigarette smoke for 4 weeks, while those of group III were exposed to cigarette smoke for 4 weeks then the exposure was stopped for another 4 weeks. Exposure to cigarette smoke resulted in affection of the coronaries. Some cardiac muscle fibers showed vacuolated cytoplasm, while other showed deeply stained acidophilic cytoplasm and psychotic nuclei. Scanning electron microscopic examination showed that some cardiac muscle fibers appeared necrotic with loss of their normal architecture. There was a decrease in succinic dehydrogenase enzyme activity and in the antiapoptotic Bcl-x [L]protein expression. Stopping the exposure for 4 weeks showed that few cardiac muscle fibers were still affected. Areas of fibrosis were seen between the cardiac muscle fibers in Mallroy stained sections and in the scanning electron microscopic study. There was an increase in scenic dehydrogenase enzyme activity and in the Bcl-x[L] protein expression in the cardiac muscle fibers in group III- that was left for 4 weeks for recovery after 4 weeks of exposure to cigarette smoke- in comparison to those of group II, but was still less than those of the control It is concluded that cigarette smoke affected the cardiac muscle and some of its effects could not be reversible