Cardiac oxidative stress is elevated at the onset of dilated cardiomyopathy in streptozotocin-diabetic rats

The association between nitric oxide synthase (eNOS and iNOS) status, oxidative stress, and cardiac function was evaluated in streptozotocin (STZ)-diabetic rats to understand the etiology of diabetic cardiomyopathy. Cardiac function was determined by echocardiography. eNOS and iNOS status and superoxide production were assessed by immunohistochemistry and chemiluminescence, respectively. In STZ-diabetic rats, stroke volume, cardiac output, and left ventricular ejection fraction were significantly lower than in controls (CT, P < .05), whereas left ventricular end-systolic volume was higher. Cardiac NOS activity increased from 161 +/- 18 cpm/mg tissue in CT rats to 286 +/- 20 cpm/mg tissue (P < .001) in STZ-diabetic rats. Furthermore, superoxide production and cardiac eNOS and iNOS levels were higher in STZ-diabetic rats than in CT rats (P < .05). An increased activation of cardiac eNOS and iNOS is observed concomitantly with decreased cardiac function. Thus, increased oxidative stress in the heart may be implicated in the development of dilated cardiomyopathy in STZ-diabetic rats.