Experimental Diabetes and the Lung: I. Changes in Growth, Morphometry, and Biochemistry

Diabetes induced by streptozotocin at 3 wk of age in rats resulted in diminished somatic growth by 7 wk of age. Specific lung volume and weight (volume or weight per 100 gram body weight) were increased. The amount of lung DNA was decreased, and collagen and elastin were increased. The volume proportion of alveolar walls was increased at the expense of alveolar air. Air spaces were diminished in size, and alveoli increased in number. Total phospholipids and disaturated phosphatidylcholine (DSPC) were decreased, but they were normal relative to alveolar surface area. These changes reverted towards normal as a result of insulin treatment. Rats matched in weight (undernourished animals) for the diabetic animals showed relative preservation of lung weight, increased DNA, and reduced nonconnective tissue protein, RNA, collagen, and elastin. Air spaces were enlarged, alveolar surface area was decreased, and alveoli were decreased in number. Total phospholipids and DSPC were decreased, but normal when expressed per alveolar surface area. We conclude that diabetes and undernourishment have different effects on connective tissue synthesis in the lung that affect lung growth and structure, providing further evidence for the "fishnet" hypothesis of alveolar growth.