Oxidized low-density lipoproteins and microvascular responses to ischemia-reperfusion.

The objective of this study was to determine whether ischemia and reperfusion (I/R) and/or chronic arterial hypertension potentiates the leukocyte-endothelial cell adhesion (LECA) and microvascular dysfunction elicited by oxidized low-density lipoproteins (ox-LDL). Mast cell degranulation, leukocyte adherence and emigration, and albumin leakage were monitored in postcapillary venules of rat mesentery. Intra-arterial infusion of copper-oxidized LDL (Cu-LDL), at a concentration that does not directly affect the microvasculature, significantly enhanced the I/R-induced recruitment of adherent and emigrated leukocytes but does not affect the increased albumin leakage and mast cell degranulation responses normally observed after I/R. Infusion of a higher concentration of Cu-LDL in nonischemic mesentery of either normotensive Wistar-Kyoto or spontaneously hypertensive rats elicited significant yet similar increases in LECA, mast cell degranulation, and albumin leakage. These findings indicate that 1) ox-LDL act synergistically with I/R to promote leukocyte recruitment in postcapillary venules but without an accompanying exacerbation of albumin leakage, and 2) ox-LDL do not elicit a more intense inflammatory response in the microvasculature of hypertensive versus normotensive animals.