DIFFERENTIAL MONOCYTIC CELL ADHERENCE TO SPECIFIC ANATOMIC REGIONS OFTHE CANINE AORTA

Circulating monocytes and vascular endothelial cells (EC) interact in a complex and dynamic manner that varies between vascular beds. The ob jective of this study was twofold: to ascertain if monocytic cell adhe sion to vascular endothelium differed between specific anatomic region s of the canine aorta, and to investigate the effect of known EC stimu lators on monocytic cell adhesion to cells from these regions. Initial in vitro studies measuring adherence of U937 cells, a human monocytic cell line, to canine jugular vein and aortic EC monolayers revealed a dose-dependent increase in adhesion to EC stimulated with interleukin -1 (IL-1), lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate ( PMA), or thrombin. While there was no regional difference in monocytic cell adherence to unstimulated EC in tissue culture, studies demonstr ated greater monocytic cell adhesion to stimulated EC cultured from th e distal versus proximal aorta. In organ culture, unstimulated adhesio n of U937 cells or autologous monocytes was significantly greater to t he distal aorta than the proximal aorta. Although monocytic cell adhes ion to both the proximal and distal aorta increased with stimulation, the percentage increase in the proximal aorta, 1,086% with IL-1, 237% with PMA, 209% with LPS, and 174% with thrombin, was greater than in t he distal aorta, demonstrating a significant functional difference in the endothelium from separate anatomic regions of a single vessel. Thi s may have a direct relevance to the regional specificity of vascular disease.