ACTIVATION OF ENDOTHELIAL-CELLS DURING INSULIN-DEPENDENT DIABETES-MELLITUS - A BIOCHEMICAL AND MORPHOLOGICAL-STUDY

Plasma membrane lipid dynamics and cellular morphology were evaluated in endothelial cells obtained from umbilical cords of five women affec ted by insulin-dependent diabetes mellitus (IDDM) and six healthy preg nant women of similar age and gestational age. Endothelial cells were prepared by an adaptation of the method of Jaffe et al. Membrane fluid ity was studied by means of the steady-state fluorescence anisotropy ( r) of (4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), a fluorescent probe specifically anchoring at the membrane surface. Flui d phase endocytosis was evaluated by the measurement of the changes in fluorescence intensity of TMA-DPH at various times, owing to the inte rnalization of the fluorescent marker in endocytic vesicles. The morph ological and morphometric studies were performed by means of transmiss ion electron microscopy (TEM). Endothelial cells obtained from IDDM wo men showed: (a) increased fluidity of the superficial region of the pl asma membrane; (b) a more active fluid phase endocytosis compared with cells from healthy women; (c) increase in mitochondrial area, Weibel- Palade bodies and rough reticulum with wide cisternae. No statisticall y significant correlation was found between metabolic control and memb rane fluidity and endocytosis. All the observed modifications suggest the presence of endothelial cell activation with membrane reshaping du ring IDDM. These alterations might play a central role in the pathophy siology of atherosclerosis and microangiopathy associated with diabete s mellitus.