EARLY INCREASE PRECEDES A DEPLETION OF ENDOTHELIN-1 BUT NOT OF VON-WILLEBRAND-FACTOR IN CUTANEOUS MICROVESSELS OF DIABETIC-PATIENTS, A QUANTITATIVE IMMUNOHISTOCHEMICAL STUDY

Endothelin-1 (ET-1) is a vasoconstrictor peptide which is produced by endothelial cells. The subcellular distribution of ET-1 in human skin and the variation of immunostaining for ET-1 by light microscopy in sk in biopsies of diabetic patients have been analysed using immunohistoc hemistry and image analysis quantification. Skin biopsies were collect ed from 17 patients with type 1 diabetes of different durations and wi th presence or absence of microangiopathy in the retina; skin biopsies of healthy subjects were utilized as controls. The distribution of ET -1 immunoreactivity (IR)at both light and electron microscopy was comp ared to that of von Willebrand factor (vWf), a general marker of total cutaneous microvessels. Immunohistochemistry revealed that in control s the distribution of immunostaining was similar for ET-1 and vWf, bei ng localized to microvessels in all areas of the skin. However, at the electron microscopical level ET-1-IR was localized in the endothelial cytoplasm rather than in specific organelles, while vWf immunostainin g was associated with Weibel-Palade bodies. ET-1-IR was observed in 4/ 8 (50 per cent) biopsies from healthy subjects; this increased to 81.8 per cent in biopsies of patients affected by diabetes for less than 1 0 years and decreased to 16.6 per cent in patients with diabetes for m ore than 10 years. Quantification of ET-1 staining showed a significan t decrease of ET-1-IR in patients affected by diabetes for more than 1 0 years compared with those affected by diabetes for less than 10 year s (P<0.05). Also, the percentage of biopsies showing positive ET-1 sta ining was lower in patients with retinopathy than in patients without retinopathy. On the contrary, vWf-IR was observed in all skin specimen s and its quantification showed no differences between diabetic patien ts and controls. These changes are not related to variations in the nu mber of blood vessels, and it is suggested that they reflect a possibl e functional alteration of the endothelial cells during diabetes.