The present work deals with the effect of two doses of melatonin (low dose of melatonin, 100 mg/kg/30 days and high dose of melatonin, 200 mg/kg /30 days) on alloxanized diabetic adult rats. The pancreas of control rats showed normal acinar and islet cells. The pancreas of diabetic rats demonstrated histopathological disorders (by using H&E). These lesions included atrophy of acinar cells, vacuolation of the cytoplasm in some areas and widening of the lumens. The islets of Langerhans exhibited signs of leucocytic infiltration, dilatation of blood vessels and vacuolation of cytoplasm in many islet cells. The collagenous fibres (by using azan stain) increased around blood vessels and intercalated ducts. The cytological study demonstrated that the pancreatic exocrine portion of the diabetic rats exhibited an increase in the number of light acinar cells, a decrease in the number of dark cells and reduction in zymogen granules, dilatation in rER, destruction of mitochondria and irregularity of nuclei. The islets of Langerhans showed destruction of pancreatic beta cells with marked dissolution of beta granules and degeneration of mitochondrial cristae. Irregular nuclei with vacuolar balloon-like nuclear envelopes were seen. The alpha cells did not undergo notable structural modifications and they appeared to increase in number with their cytoplasm filled with secretory granules. The treatment of diabetic rats with low dose of melatonin improved the architecture of the pancreatic acinar and islet cells, while no improvement could be demonstrated in the pancreatic tissue with the high dose of melatonin treatment.
Key words: Pancreas, Histology, Cytology, Melatonin, Diabetes, Rats
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