Differences in microvascular fluid permeability between long-duration type I (insulin-dependent) diabetic patients with and without significant microangiopathy.

1. To further investigate the role of microvascular functional changes in the pathogenesis of diabetic microangiopathy in type 1 diabetes, microvascular fluid permeability was measured in nine patients with a long disease duration and no or minimal (background retinopathy alone) microangiopathy, nine age-, sex- and duration-matched patients with microalbuminuria and nine control subjects. Microvascular fluid permeability was assessed by determination of the forearm capillary filtration coefficient using a sensitive strain-gauge plethysmographic technique. 2. Microvascular fluid permeability was significantly higher in the patients with microalbuminuria [8.5 (6.8-15.2) x 10(-3)ml min-1 100g-1 of tissue mmHg-1; median (range)] than in the patients with no or minimal complications [5.2 (3.6-7.0) x 10(-3) ml min-1 100g-1 of tissue mmHg-1, P < 0.001]. There was, however, no significant difference in microvascular fluid permeability between the patients with no or minimal complications and control subjects [4.5 (3.2-5.7) x 10(-3) ml min-1 100g-1 of tissue mmHg-1, P = 0.31]. Blood pressure and glycaemic control were similar in the two groups of diabetic patients. 3. These results provide further evidence that changes in microvascular permeability are found in other vascular beds in patients with incipient nephropathy, whereas no such changes are found in patients with a long disease duration and little evidence of microangiopathy.