MONOCYTE CHEMOTACTIC PROTEIN-1 INCREASES COLLATERAL AND PERIPHERAL CONDUCTANCE AFTER FEMORAL-ARTERY OCCLUSION

Monocytes are activated during collateral artery growth in vivo, and m onocyte chemotactic protein-1 (MCP-1) has been shown to be upregulated by shear stress in vitro. In order to investigate whether MCP-I enhan ces collateral growth after femoral artery occlusion, 12 rabbits were randomly assigned to receive either MCP-1, PBS, or no local infusion v ia osmotic minipump. Seven days after occlusion, isolated hind limbs w ere perfused with autologous blood at different pressures, measuring f lows at maximal vasodilation via flow probe and radioactive microspher es, as well as peripheral pressures. This allowed the calculation of c ollateral (thigh) and peripheral (lower limb) conductances from pressu re-flow tracings (slope of the curve). Collateral growth on postmortem angiograms was restricted to the thigh and was markedly enhanced with MCP-1 treatment. Both collateral and peripheral conductances were sig nificantly elevated in animals with MCP-1 treatment compared with the control group, reaching values of nonoccluded hindlimbs after only 1 w eek of occlusion (collateral conductance, 70.6+/-19.23 versus 25.1+/-2 .59 mL/min per 100 mm Hg; P<.01; peripheral conductance, 119.3+/-22.37 versus 45.4+/-6.80 ml/min per 100 mm Hg; P<.05). These results sugges t that activation of monocytes plays an important role in collateral g rowth as well as in capillary sprouting.