5th Research EFFECT OF CYCLOSPORINE A ON THE PANCREAS IN RABBITS: A LIGHT AND AN ELECTRON MICROSCOPIC STUDY Fathy Ahmed Fetouh, Eman M.A. Abdelghany Department of Anatomy, Faculty of Medicine, Zagazig University ZUMJ Vol (14) No(3) July 2008: 2271-2288 ABSTRACT Objective: The present work aimed to study the histological and ultrastructural effects of cyclosporine A on the exocrine and endocrine parts of the pancreas. Materials and Methods: 2 groups of Egyptian adult rabbits were used for this study (3-4 rabbits for each). One group was used as a control and the other group (experimental) was treated with cyclosporine A as oral solution in a dose of 15 mg/kg for 10 days. The animals were killed by cervical dislocation and the pancreatic specimens were taken from tail of the pancreas. The specimens were fixed in a buffered glutaraldehyde 2.5% solution. Semi-thin sections of 1 m thick were obtained, stained with 1% toluidine blue and examined by light microscopy and ultrathin sections for electron microscopic examination. Results: The cyclosporine A had adverse effects on the pancreas. The acinar cells showed marked decrease in their zymogen granules and some showed degranulation at their apices. Abundant cytoplasmic vacuoles were observed. The rough endoplasmic reticulum was decreased swollen and vacuolated. The mitochondria were few and degenerated with no transverse cristae. The nucleus was deformed, irregular and dark. In islet cells, the beta cell showed marked decrease in its secretory granules, the mitochondria were observed as numerous and elongated. The endoplasmic reticulum appeared as few scattered stacks. The alpha cells were not affected structurally and appeared with their normal secretory granules and endoplasmic reticulum. Conclusion: Cyclosporine A has adverse effects on the pancreas and sudden onset of diabetes mellitus or acute pancreatitis should always be a concern in the management of cyclosporine A treated patients. Key words: Cyclosporine A, Pancreatic acini, Pancreatic islets, Ultrastructure