ALTERATIONS IN THE ULTRASTRUCTURE OF NON-CILIATED BRONCHIOLAR EPITHELIAL (CLARA) CELLS BY STREPTOZOTOCIN-INDUCED DIABETES IN RATS

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Abstract
Marked alterations in type II pneumocyte ultrastructure occur in streptozotocin-induced diabetes. To see whether other pulmonary epithelium is affected, terminal bronchioles were examined by transmission electron microscopy. Adult male rats (10) received 1 intrajugular injection of streptozotocin (75 mg/kg of body weight) and were killed 14 days later. As control subjects, 5 additional rats received saline only, and 5 rats given streptozotocin injections received protamine zinc insulin (1 unit/rat per day). Compared to lungs of control animals, the bronchiolar epithelial cell type most altered in diabetic rat lungs was the Clara cell. The numbers of ovoid secretory granules decreased significantly (29 of 57 cells were without granules vs. 0 of 78 in control animals), and the number of rod-shaped granules increased. Administration of exogenous insulin alleviated the changes. Changes in pulmonary metabolic function associated with diabetes mellitus result from alterations not only in granular pneumocytes, but also in nonciliated, bronchiolar secretory epithelial (Clara) cells.