Differences in arterial and arteriolar endothelial structure during endotoxin shock.
Previous studies of physiological and ultrastructural assessment changes in the walls of the femoral artery and A1, A2, and A3 arterioles in the rat cremaster muscle after infusion of Escherichia coli endotoxin (ENDT) (6 mg/kg-1 hr. period) indicate there may be a difference in the alteration of the endothelial structure of arteries and arterioles. Functionally, ENDT has been shown to abolish acetylcholine (ACh)-induced relaxation in the femoral artery [Zhou, PhD dissertation, University of South Florida, Tampa, 1992]. Dilations of A1 arterioles were shown to be reduced, but dilations of A2 and A3 arterioles were not significantly changed from control [Baker and Sutton, Am J Physiol, 264:H 1118-H 1123, 1993]. In the current study, ultrastructural evaluation of femoral arterial tissue post-ENDT at the mean arterial pressure (MAP) of 100 mm Hg revealed partially destroyed endothelial cells. The MAP decreased as the animal progressed into shock. At 80 mm Hg, 60 mm Hg and 40 mm Hg, essentially all endothelial cells were destroyed, with the internal elastic lamina denuded. In contrast, endotoxin damage in the A1, A2, and A3 arterioles was minimal even at a MAP of 40 mm Hg. Endothelial cells of A1 arterioles post-ENDT had more vacuoles than at control. Therefore, arteriolar endothelium was functionally and anatomically relatively undamaged, consequent to endotoxin administration, in contrast to femoral arteries where the endothelium was destroyed in a short time.