Reduced pulmonary endothelium-bound angiotensin converting enzyme activity in diabetic rabbits.

We examined the effects of diabetes on pulmonary capillary endothelial cell (EC) function in diabetic rabbits. One, three and six weeks after alloxan treatment, rabbits were anesthetized and pulmonary endothelium-bound angiotensin converting enzyme (ACE) activity was estimated from the single-pass transpulmonary hydrolysis of benzoyl-Phe-Ala-Pro (BPAP), an ACE specific substrate. ACE activity significantly decreased in 1- and 3-week diabetic rabbits and returned to control levels at 6 weeks. Capillary dilation, parenchymal hemorrhage and erythrocyte clumping were maximal in 3-week diabetic rabbits. We conclude that in the alloxan-diabetic rabbit, there are transient functional and more persistent morphological alterations.