Prior exercise training increases collateral-dependent blood flow in rats after acute femoral artery occlusion

We evaluated whether prior training would improve collateral blood flow (BF ) to the calf muscles after acute-onset occlusion of the femoral artery. Ex ercise training was performed in the absence of any vascular occlusion. Adu lt male Sprague-Dawley rats (similar to 325 g) were kept sedentary (n = 14) , limited to cage activity, or exercise trained (n = 14) for 6 wk by treadm ill running. Early in the day of measurement, animals were surgically prepa red for BF determination, and the femoral arteries were occluded bilaterall y. Four to five hours later, collateral BF was determined twice during trea dmill running with the use of Ce-141 and Sr-85 microspheres: first, at a de manding speed and, second, after a brief rest and at a higher speed. The ab sence of any further increase in BF at the higher speed indicated that maxi mal collateral BF was measured. Prior training increased calf muscle BF by similar to 70% compared with sedentary animals; however, absolute BF remain ed below values previously observed in animals with a well-developed collat eral vascular tree. Thus prior training appeared to optimize the use of the existing collateral circuit. This implies that altered vasoresponsiveness induced in normal nonoccluded vessels with exercise training serves to impr ove collateral BF to the periphery.