Résumé
A strong relationship between aging and diabetes mellitus has been clinically suggested, however, none of the previous published data had clearly focused on the age-related cytomorphological changes in the pancreas which are the goal of this study. Three groups of male apparently healthy rabbits have been used, ten animals each; classified as group-1 [3-5months old]; group-2 [9-12 months old] and group-3 [24-36 months old]. After sacrification, sections from the pancreas were stained by Haematoxylin and Eosin [H and E], Gomori trichromic stain and ultrastructurally to detect aging histologic changes as well as immunohistochemically to identify insulin and glucagon secreting cells using their appropriate monoclonal antibodies. A progressive histological distortion with fibrosis and fatty changes were directly proportional to age, being mild in group-2 and severe in group-3. Morphometric studies by computerized image analysis showed that the mean number of islets was significantly higher in group2 [8.98+/-1.51], lowest in group-1 [5.08+/-1.48] and intermediate in group-3 [6.37+/-1.37]. The mean diameter and square area of islets were significantly higher in group-2 compared to other groups [P< 0.05]. The mean number of beta cells per islet and their secretary granules were significantly [P <0.05] higher in group-2, intermediate in group-1 and lowest in group-3.In contrast, the mean number of alpha cells per islet and their secretory granules were insignificantly [P< 0.05] higher in group -2, intermediate in group-3 and lowest in group-1.Also, the beta/alpha ratio [beta cells/alpha cells] was greatest in group-2 [3.059:1], intermediate in group-1 [3.37:1], and lowest in group-3 [2.479:1]. The increased number of beta cells may be due to a compensatory process to correct the hormonal feedback mechanism of insulin .The results of this work suggest that beta cells are generally more vulnerable to aging, an observation which might be correlated clinically with higher incidence of diabetes in older ages