MICROVASCULAR RESPONSE TO TISSUE-INJURY AND CAPILLARY ULTRASTRUCTURE IN THE FOOT SKIN OF TYPE-I DIABETIC-PATIENTS

1. Microvascular blood flow responses to injury and capillary ultrastr ucture were assessed by laser Doppler flowmetry and detailed light and electron microscopy respectively in skin biopsied from 28 patients wi th insulin-dependent diabetes and 17 control subjects. 2. The hyperaem ic response induced by biopsy (P<0.001) and heating to 44 degrees C (P <0.001) was significantly lower in the diabetic patients and showed pr ogressive impairment with the severity of complications (P<0.001). 3. Skin capillary basement membrane thickness was significantly increased in the diabetic patients (P<0.001) and also increased with the severi ty of complications (P<0.002). Both the luminal area (P<0.001) and the endothelial cell outer perimeter (P<0.002), measures of luminal and c apillary size, respectively, were significantly reduced in all diabeti c patients. 4. Basement membrane thickness was related significantly t o the impaired hyperaemic response to both biopsy (P<0.01) and thermal injury (P<0.01). 5. Our findings support the hypothesis that structur al abnormalities, which are characterized by an early reduction in cap illary size and later thickening of basement membrane, form an importa nt mechanism for the impaired hyperaemic response in diabetic patients .