Blood entering and leaving tibiae of normal dogs and dogs in states of low bone remodeling and high bone remodeling (hypoparathyroidism, hypothyroidism, hyperparathyroidism, and hyperthyroidism) was analyzed for ten-minute 85Sr clearances, arteriovenous differences in oxygen content, partial pressures of oxygen and carbon dioxide, and pH. The arteriovenous differences in oxygen content of tibial blood were the same in high, normal, and low-remodeling states. 85Sr clearance was decreased in dogs with low-bone remodeling and increased in dogs with high-bone remodeling.
The close adjustment of osseous blood flow, as indirectly determined by 85Sr clearance, with remodeling activity and the constant oxygen uptake indicate the importance of alterations in blood flow in meeting the increased nutritional demands of active tissues. These adjustments of blood flow through bone to changing nutritional needs suggest a metabolic factor linking flow to the tissue's need for nutrients.