Use of tracer microspheres to measure bone blood flow in conscious dogs

Abstract

Blood flow was measured in mature and immature dogs by means of tracer microspheres. Microspheres of 15 micron were found to be the most suitable size in the dog. Total body nonentrapment in the awake, standing dog is likely to be less than 10%. Cortical bone flood flow, devoid of periosteum and marrow, is 2.5 ml/100 g/min in mature dogs and 7.0 ml/100 g/min in immature dogs, P < 0.005. Blood flow in cancellous bone is greater than that in cortical bone in mature (P < 0.001) and immature (P < 0.02) dogs. Flow is different in different regions of a long bone because of different proportions of cortical and cancellous bone, probably because of interrelationships of function (surfaces undergoing remodeling) and, therefore, of energy metabolism and blood flow.

Transcapillary exchange and retention of fluoride, strontium, EDTA, sucrose, and antipyrine in bone

“…It is recognized that a tracer injected into the nutrient artery will reach the capillary beds of marrow tissue as well as bone tissue. However, studies with microspheres indicate that the percentage of blood flow to bone tissue in a mature dog tibia is approximately 89%-that is, flow in the tibia is mainly to bone [31]. Thus we do not believe that the presence of blood flow to marrow influences our interpretation.…”

“…In the last three sets of experiments, a 1-to 2-s injection of 0.25 ml of injectate was followed by a short flush of 0.1 ml. In the first three sets of experiments, the tracer was injected as an extended bolus at a constant rate into the distal segment; this was done because the blood flow through the tibial diaphysis is collateral flow of about 2.5 ml/100 g/ min, estimated from clearance values corrected by net extraction [1] or estimated by microspheres in standing, conscious dogs [9]. Further, we wished to keep injectate flow to a modest fraction of the total in order to avoid disturbing the rate of flow or the perfusion pressure.…”

Hemodynamics of the juvenile knee

“…Animals with a major growth potential such as Labrador breeds were preferred to facilitate growth studies (V). Furthermore the dog has a chondroosseous structure and circulation which is close to the human (Rhinelander 1976, Eitel et al 1981, and the circulation in the adult and immature dog bone is well elucidated (Morris & Kelly 1980, T~ndevold 1983. In order to minimize interindividual variation, puppies from the same litter were used ignoring sex differences.…”

“…Both catheters were inserted via the carotid arteries, which were ligated. This instrumentation has also been used in studies in awake dogs (Morris & Kelly 1980, T6ndevold & Bulow 1983. Carotid arterial ligation might, however, influence the carotid baroreceptors and alter sympathetic nervous system activity (Kirchheim 1976).…”

“…The immature skeleton receives approximately 10% of the cardiac output at rest (Gross et al 1979, Morris & Kelly 1980. Immature bone exhibits internal structural and circulatory differences, which change by development and growth .…”