Blood flow distribution in tissues of perfused rat hindlimb preparations.

Aerobic muscle metabolism during concentrations requires adequate blood flow and oxygen delivery. Since the perfused rat hindquarter (HQ) has become widely used for muscle stimulation, we examined the blood flow distribution, using 15 microns radiolabeled microspheres, and oxygen consumption of the HQ, using different commonly used perfusion protocols. Perfusion via the abdominal aorta resulted in well-matched (r = 0.90) blood flows between tissues of both hindlimbs that were proportional to total perfusion inflow. Blood flows to the high-oxidative fast-twitch and slow-twitch red muscle sections were three- to fourfold greater than flows to sections of low-oxidative fast-twitch white muscle. However, a large fraction (28%) of the total inflow went to the trunk region, even though all apparent arterial branches to the trunk region were ligated. This trunk mass accounts for at least 40% of the total metabolic responses of the HQ and diverts a large blood flow that is often presumed to supply the hindlimbs. As a result, muscle performance of the distal hindlimb muscle during stimulation can be inordinately poor. Ligation of the iliac artery to the contralateral limb improves blood flow to the remaining hindlimb but does not eliminate trunk blood flow. In contrast, perfusion via the femoral artery restricted 95% of the inflow to the single hindlimb, thereby reducing the tissue mass perfused. Blood flow to the distal limb musculature was high, resulting in an enhanced muscle performance. Thus single hindlimb perfusion provides a preparation where the contracting muscle is a large fraction of the total tissue, and the venous effluent better reflects the metabolic events in the contracting muscle.(ABSTRACT TRUNCATED AT 250 WORDS)