Renal arterioles in patients with type I diabetes and microalbuminuria before and after treatment with antihypertensive drugs

Antihypertensive drugs can slow or even reverse the progression of diabetic nephropathy at the microalbuminuric stage. This study was performed to obtain quantitative data on changes in the renal arterioles in a follow-up study. Twelve patients with type I diabetes and with microalbuminuria were allocated to treatment for 3 years with either an ACE inhibitor (group I, 6 patients) or a beta blocker (group II, 6 patients). Baseline and follow-up renal needle biopsy specimens were taken and serially sectioned at 1 mu m for light microscopy, enabling identification of arterioles as afferent or efferent. Thin sections for electron microscopy were made at 50-mu m intervals, and micrographs were taken of arteriolar profiles. Matrix volume fraction of the media and a calculated matrix thickness were obtained. At baseline, structural parameters were higher than normal values. At follow-up all patients were normoalbuminuric. Both groups showed only minor changes in arteriolar structures over 3 years. In the afferent arterioles in group II there was a significant increase in the matrix volume fraction of the media, and there was a tendency to an increase in matrix thickness in both groups. In the efferent arterioles there were no significant changes in parameters. There were no differences between the two groups in arteriolar structural changes from baseline to follow-up. Thus. this study shows a slight but significant matrix accumulation in the afferent arterioles during treatment with antihypertensive drugs. This may have implications for the progression to overt nephropathy, which indicates a need for more long-term studies of treatment with antihypertensive drugs in incipient nephropathy in type I diabetes.