Dynamic changes in the microcirculation of diabetics as related to diabetic microangiopathy.

Reversible abnormalities of many vascular beds have been observed in early diabetes, before irreversible structural changes of diabetic microangiopathy became apparent. In the bulbar conjenctiva and in the kidney the changes are associated with vascular dysfunction and may be due to autonomic neuropathy. The role of autoregulation in these vascular beds is not clear. In the limb muscles and in the retina the functional abnormality in early diabetes and in those with only mild retinopathy is increased blood flow. This increase in blood flow is probably the result of autoregulatory adaptation to hypoxia induced by 2,3 diphosphoglycerate deficiency. Lactic acid accumulation may also contribute. Breakdown of the autoregulation in the retina results in the development of diabetic retinopathy. The late stages of retinopathy, new vessel formation, are an attempt at revascularisation of areas of capillary non-perfusion.