Since a number of recent studies have indicated that diabetes mellitus depresses pulmonary phospholipid and protein synthesis, we examined the effects of experimental diabetes mellitus on the granular (type II) pneumocyte. Eleven adult male Sprague-Dawley rats were made diabetic by a single intravenous injection of streptozotocin (75 mg. per kg. of body weight); they were killed 14 days later. Five of the rats received daily subcutaneous injections of protamine zinc insulin (1 unit per rat per day) for either 2 or 7 days prior to killing. Five additional rats received saline minus streptozotocin. Lung tissue from all rats was examined by transmission electron microscopy. Compared to control rat lung, the most affected cell type in the parenchyma of the diabetic rat lung was the granular (type II) pneumocyte. The major change was dilation of the granular endoplasmic reticulum. This ranged in degree from massive changes which occupied large portions of the cell cytoplasm to focal dilations associated with normal appearing granular endoplasmic reticulum. The cisterna of this reticulum was filled with a fine granular material which was lower in electron density than the surrounding cytoplasm. Of the 81 granular pneumocytes examined in diabetic rat lungs, 67 had dilated granular endoplasmic reticulum. No alteration in lamellar body number was observed. Therapy with exogenous insulin eliminated the change, indicating that the massive dilation in granular endoplasmic reticulum is the direct result of insulin deprivation. These findings demonstrate that the depression in pulmonary metabolic function associated with diabetes mellitus results from alterations in the granular pneumocyte and that, among all of the cell types in the pulmonary parenchyma, the granular pneumocyte is the cell that is most dependent on insulin for normal metabolic function.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Jan 1 1978|
ASJC Scopus subject areas
- Pathology and Forensic Medicine
- Molecular Biology
- Cell Biology