Early ultrastructural changes of myocardial endothelial cells in traumatic haemorrhagic shock in rats.

The aim of this study was to assess early traumatic haemorrhagic shock (THS)-induced changes in myocardial endothelial cells (mECs) both morphologically and morphometrically. The mECs of capillaries of the left ventricular myocardium were investigated by electron microscopy 15, 30, 60, and 120 min after a standardised THS and compared to a control group. With the use of a computer-assisted image analysis system, we measured the following morphometric parameters--height, area, circumference, cytoplasmic processes, and interendothelial junctions--and determined the number and distribution of cytoplasmic vesicles in every mEC. THS induced a significantly increased formation of cytoplasmic processes and a redistribution of cytoplasmic vesicles towards the cell centre, with the changes peaking between 15 and 60 min. There was no evidence of an increase in mEC height or area/circumference ratio used as indicators for early mEC oedema, although the latter dropped significantly after 15 min. No increase in damaged mitochondria was observed and the interendothelial junctions remained close. The THS-induced ultrastructural changes represent early mEC activation. Irreversible damage of mECs does not occur.