Disturbances in microvascular function were studied by measurement of capillary diffusion capacity (CDC), capillary filtration coefficients (CFC) and resting and hyperemic skeletal muscle blood flows in normal persons and patients with prediabetes and diabetes with and without microangiopathy. Blood flow, CDC and CFC were determined by calf venous-occlusion plethysmography and 133Xe and 131l clearances from hyperemic anterior tibial muscle. Diabetic patients with microangiopathy had significantly larger CDC's and 131l clearances than the normal controls (p less than 0.01) and diabetic patients without microangiopathy (p less than 0.05). Normal persons had hyperemic muscle flows (133Xe) significantly greater than those in the other groups (p less than 0.05). Resting flows and CFC's did not differ significantly among the groups. Three of 11 prediabetic subjects had very abnormal CDC's. The finding of normal CFC and abnormal CDC in diabetic patients with microvascular disease suggests that small vessels are abnormally permeable to ions, and that the increased CDC is not due to increased surface area of the microvasculature. CLINICIANS have known for a long time that microangiopathy, as manifested by retinopathy, neuropathy and nephropathy, develops in patients with diabetes mellitus. Specific morphologic changes in the microvascular beds are considered to correlate with the clinical abnormalities of vision, sensation and renal function.1 These changes include thickening of vessel basement membranes and periendothelial deposition of PAS-positive material; they have been noted in arterioles, capillaries and veuilles of different tissues in established diabetes and even in some prediabetic subjects.1 Recently, physiologic abnormalities of the microcirculation have been reported in patients with long-term juvenile diabetes with the aid of radioactive tracers and.
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