Evaluation of time dependent changes of the rat's lung in experimentally induced diabetes mellitus: light and electron microscopic study

ABSTRACT

Diabetes mellitus is a chronic metabolic disease characterized by persistent hyperglycemia. This a major health problem that is associated with a number of serious, sometimes life-threatening complications. There has been increasing evidence that the respiratory functions of patients with diabetes are impaired in the course of their disease. This work aimed to study structural changes of the rat's lung in experimentally induced diabetes and evaluation of these changes in relation to duration of diabetes. Thirty adult male albino rats were divided into three groups, Group I served as control group. Group II consisted of two equal subgroups of rats [lb and lib], which received citrate buffer. Group Ill included two equal subgroups [IIIa and IIIb], which were subjected to induction of diabetes by using streptozotocin [STZ]. Subgroups IIa and IIIa were sacrificed after four weeks from the experiment while subgroups Jib and Tub were sacrificed after eight weeks. Blood samples were collected three times during the experiment to measure the blood glucose level. At the end of the experiment, the lungs were dissected out and the specimens were prepared for light and electron microscopic study. Morphometric analysis was also done to confirm the results. After 4 weeks of induction of diabetes, there was significant increase in the thickness of interalveolar sepia which showed cellular infiltration. Some bronchioles showed patchy areas of hyperplasia of theft lining epithelium. After 8 weeks of induction of diabetes, the lung revealed accumulation of large number of alveolar inacrophages and inflammatory cells in the pulmonary interstitium leading to highly significant increase in the thickness of interalveolar sepia and collapse of many alveoli with loss of normal architecture of the lung parenchyma. Congestion of the blood vessels and thickening of their walls could be seen with exiravasation of RBCs and fluid exudates in the interstitium. There was increased deposition of collagen fibres by increasing duration of diabetes. Electron microscopy revealed significant increase in the mean number of type II pneumocytes which showed progressive degenerative changes with increasing duration of diabetes.It could be concluded that, diabetes induced structural changes of the lung which increased progressively and became much worse with increasing duration of diabetes. So much attention should be directed to early diagnosis and treatment of diabetes to avoid or postpone onset of complications