Selection of an ACE Inhibitor as the Comparative Agent Findings in preclinical studies of animals with diabetes mellitus suggest that ACE inhibitors reduce glomerular damage by one or more mechanisms independent of their antihypertensive effects. Glomerular efferent arteriolar tone is increased in diabetic animals and as a result there is an increase in transcapillary hydraulic pressure. These alterations may decrease the functional integrity of the glomerular capillary wall. In rats with diabetes, the long term administration of an ACE inhibitor diminishes the functional and morphologic evidence of glomerular injury and decreases glomerular transcapillary pressure. Removal of the tonic constrictor effect of angiotensin II on efferent arterioles would be expected to lower glomerular intracapillary pressure while preserving renal plasma flow.