EARLY ADAPTATIONS IN COLLATERAL AND MICROVASCULAR RESISTANCES AFTER LIGATION OF THE RAT FEMORAL-ARTERY

Collateral and microvascular (including feed artery) resistances in th e rat hindlimb were determined immediately or 1 wk after ligation of t he femoral artery. Collateral-to-microvascular resistance ratios were determined from in vivo pressure measurements proximal and distal to t he ligation. Microvascular resistance was 32 +/- 2.5 and 41 +/- 1.5% o f the total collateral-dependent vasculature in acutely and chronicall y ligated limbs, respectively, and decreased 20% in both groups during reactive hyperemia. Minimum resistances of collateral vessels and the microcirculation arising from arterial branches proximal and distal t o the ligation were determined by using a modification of the standard hindquarter perfusion technique for determining maximum vascular cond uctance. One week postligation, minimum total hindquarter resistance w as decreased by a reduction in the resistance of the collaterals (simi lar to 50%) and microcirculation (similar to 33%) proximal to the liga tion. The results suggest that the microvasculature distal to the occl usion is able to increase flow by dilation both initially and at 1 wk postligation but that collateral adaptations are primarily responsible for decreases in the minimum total resistance of the collateral-depen dent region.