Regional Vascular Volumes and Dynamic Haematocrit Compared to Regional Perfusion in Canine Cancellous and Cortical Bone

Abstract

Regional vascular volumes in different areas of long bones in dogs were measured with 12SI-fibrinogen and 51Cr erythrocytes. According to the volumes determined, the dynamic small vessel haematocrit was calculated to be 50 per cent of the arterial haematocrit in cancellous bone and 75 per cent of the arterial haematocrit in cortical bone. The perfusion rate in the same regions was determined with 99Tcm-labelled micro-spheres (size 15 μ ± 5 μ). A linear relation between perfusion rate and blood volume was demonstrated. The data obtained showed that the perfusion rate and blood volume in the red marrow in the femoral neck are 25 times greater than values obtained from tibial and femoral cortical bone. A thorough testing of the plasma indicators showed that the distribution volume in the tissue for albumin and transferrin is twice the value determined with fibrinogen. The egress of the indicators seems to be correlated with molecular weight.