Exercise training effects on collateral and microvascular resistances in rat model of arterial insufficiency.

Experiments were performed to determine if exercise training reduces collateral or microvascular resistances in the hindlimb of rats with arterial insufficiency. After right femoral arterial ligation (age 10 wk), rats were divided into sedentary (Sed) and treadmill-trained (Tr) groups (7-9 wk, final intensity: 27 m/min, 6 degree grade, 60 min/day). Minimal resistances (mmHg.ml-1.min.100 g) of the total limb (RT), collateral vessels (RC), and the microcirculations distal (Rfmc) and proximal (Rimc) to the ligation site were determined during pump perfusion of the hindlimbs. RT was lower in nonligated (open) and acutely ligated limbs of Tr than Sed rats (open: 0.69 +/- 0.011 vs. 0.93 +/- 0.071; acute: 0.92 +/- 0.028 vs. 1.18 +/- 0.070 mmHg.ml-1.min.100 g) but not in chronically ligated limbs (chronic: 0.88 +/- 0.072 vs. 1.00 +/- 0.046 mmHg.ml-1.min.100 g). RC was similar between the chronically ligated limbs of Sed and Tr rats (1.69 +/- 0.165 vs. 1.97 +/- 0.227 mmHg.ml-1.min.100 g) and was approximately 70% lower than in acutely ligated limbs of both groups. Rfmc and Rimc were not affected by arterial ligation, but Rimc was significantly lower in Tr than in Sed rats (acute: 1.05 +/- 0.026 vs. 1.54 +/- 0.163; chronic: 1.24 +/- 0.071 vs. 1.81 +/- 0.202 mmHg.ml-1.min.100 g). These results indicate that the primary site of vascular adaptations to chronic arterial ligation is in the collateral vessels. Exercise training does not significantly alter the collateralization process but may provide protection against acute arterial occlusion by stimulating microvascular growth.