Quantitative Microscopic evaluation of Melatonin treatment of Experimentally Atherosclerotic Rabbit Aorta

Abstract

Atherosclerosis is one of the most common diseases in Egypt. The exact etiology of the disease is still vague. However, Oxidative modifications of low-density lipoprotein (LDL) have been proposed to play a critical role in atherogenesis. Antioxidants have been proposed, therefore, to have a possible role in protection and/or prevention of atherosclerosis. The pineal gland hormone, melatonin, have been reported as an antioxidant. Recently melatonin has been proposed to interfere with one of the chain of events in the onset of atherosclerosis, that is, the formation of adhesion molecules. To test the role of melatonin in amelioration of atherogenesis, this work was designed to study the atherosclerosis-.related microscopic changes in the aorta of melatonin treated, high cholesterol fed rabbits. Thirty adult male rabbits were used throughout this work. The animals were fed a standard rabbit food free from cholesterol and antioxidants. The rabbits were divided into three groups each of 10 animals: Control (A) group, was raised on the ordinary diet alone for 6 weeks. Atherosclerotic induced, non treated (B) group was raised on the ordinary diet mixed with 1% cholesterol powder for a period of 6 weeks. Atherosclerotic induced, melatonin treated (C) group was raised on the ordinary diet mixed with 1% cholesterol powder and drenched 4.2 mg melatonin dissolved in saline solution daily at night for 6 weeks. The drug was given through naso-gastric tube under light ether anesthesia Paraffin sections of both control and experimental groups were prepared on the same slide. The sections were stained by haematoxylin and eosin, Masson trichrome, orcein; or periodic acid Schiff (PAS). The endothelial thickness, relative collagen, elastic fibers, smooth muscle fibers and glycosaminoglycan content in control and experimental groups were evaluated by computerized image analyzer. Statistical analysis of the results was carried out using Microsoft Excel 2000. The results revealed that the melatonin has antiatherosclerotic effects in experimental atherosclerosis in the rabbit aorta. Melatonin significantly reduced specific atherosclerotic lesions like fibrosis , smooth muscle atrophy, and decreased elastic fiber content in thoracic aortic wall. In conclusion, melatonin may be of value in the management of atherosclerosis by reducing its complications.