The effect of pentoxifylline on endothelial permeability of rabbit carotid artery wall

Weak electrical stimulation of the rabbit carotid artery wall with direct current impulses over a period of 45 min increased the endothelial permeability for horseradish peroxidase (HRP), molecular weight 40,000 Da, beneath the anode region of the electrodes. The stimuli caused a massive accumulation of the reaction products of peroxidase in the subendothelial space. With a microdensitometric technique, it was possible to quantify the amount of the peroxidase reaction products in the subendothelium, and to compare the amounts in the non-stimulated regions with those in the stimulated regions. Intravenous administration of pentoxifylline before stimulation inhibited the transendothelial transport of peroxidase. Inhibition was pronounced in the stimulated regions, whereas the uptake of HRP in the non-stimulated regions was only slightly lower than that in non-treated animals. It was demonstrated that the extent of inhibition was dose-dependent (3, 10 and 30 mg pentoxifylline/kg). Electron microscopic examination showed that the main route of permeation of HRP was through the interendothelial clefts. However, electrical stimulation also caused an increase in the vesicular uptake of HRP into endothelial cells. Both pathways seem to be influenced by pentoxifylline.