Effects of streptozotocin-induced diabetes on lung mechanics and biochemistry in rats

Young and adult rats were given a single intraperitoneal injection of 75 mg/kg streptozotocin in citrate buffer and were compared with age- and weight-matched controls that received an equal volume of buffer alone. Studies done 8 wk after the injections showed that final body weight, lung dry weight, lung DNA content, and air and saline lung volumes were significantly lower in both young and adult diabetic rats compared with the controls. In young diabetic rats, volume-pressure (V-P) curves expressed as percent maximal lung volume (%MLV) were shifted downward and to the right of those in young control rats at 5 cmH2O transpulmonary pressure (PL) for air and at 4, 6, and 8 cmH2O PL for saline-filled lungs; specific lung compliance (CL) values obtained from both air and saline V-P curves were significantly reduced, and concentration of hydroxyproline relative to DNA was significantly increased. In adult diabetic rats, V-P curves expressed in %MLV, CL values, and concentrations of protein and hydroxyproline were similar to those in adult control rats. We conclude that in both young and adult rats, diabetic state leads to somatic and lung growth retardation. In addition in young diabetic rats lung distensibility is decreased. An increase in the concentration of some connective tissue proteins may be responsible for the latter observation.