EXERCISE TRAINING EFFECTS ON COLLATERAL AND MICROVASCULAR RESISTANCESIN RAT MODEL OF ARTERIAL INSUFFICIENCY

Experiments were performed to determine if exercise training reduces c ollateral or microvascular resistances in the hindlimb of rats with ar terial insufficiency. After right femoral arterial ligation (age 10 wk ), rats were divided into sedentary (Sed) and treadmill-trained (Tr) g roups (7-9 wk, final intensity: 27 m/min, 6 degrees grade, 60 min/day) . Minimal resistances (mmHg. ml(-1).min.100 g) of the total limb (R(T) ), collateral vessels (R(C)), and the microcirculations distal (R(fmc) ) and proximal (R(imc)) to the ligation site were determined during pu mp perfusion of the hindlimbs. R(T) 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) mi n 100 g) but not in chronically ligated limbs (chronic: 0.88 +/- 0.072 vs. 1.00 +/- 0.046 mmHg ml(-1) min.100 g). Re 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 similar to 70% lower than in acutely ligated limbs of both groups. R(fmc) and R(imc) were not affe cted by arterial ligation, but R(imc) was significantly lower in Tr th an in Sed rats (acute: 1.05 +/- 0.026 vs. 1.54 +/- 0.163; chronic: 1.2 4 +/- 0.071 vs. 1.81 +/- 0.202 mmHg.ml(-1).min.100 g). These results i ndicate that the primary site of vascular adaptations to chronic arter ial ligation is in the collateral vessels. Exercise training does not significantly alter the collateralization process but may provide prot ection against acute arterial occlusion by stimulating microvascular g rowth.