Bone blood flow in conscious dogs at rest and during exercise

Using the microsphere technique bone blood flow was measured in different anatomical and functional regions in long bones in conscious dogs. The measurements were performed during physical exercise upon a treadmill, and the bone blood flow values were obtained as prework resting values after 1 and 2 hours of exercise and after 1 hour of rest. The perfusion rates increased 50 per cent from 1.6 to 2.5 ml X 100 g tissue-1 X min-1 in the femoral and tibial cortical bones during work. In the cancellous bone of the femoral head an increase from 12.6 to 20.6 ml X 100 g tissue-1 X min-1 was found. Equal flow responses were determined in the fat-filled tibia-condylar and femoral supracondylar bone. The increase took place after 2 hours' exercise, but nonstatistically verified increased perfusion was found after 1 hour's work. The alternation in bone blood flow suggests that bone has a capability of physical vasodilation during muscular work but the flow response is slow and therefore the vasodilatation seems mediated by a metabolically induced stimulus.