Short term effects of vasoactive agents and calcium regulating hormones on bone blood flow and mineral exchange in the rat

Abstract

It is now believed that there is a significant association between skeletal blood flow and the movement of other ions in and out of bone. Bone is capable ofregulation of this flow but this is affected by factors such as physiological stimuli, arterial blood pressure and humoral agents which can override this ability. The effects of vasoactive substances, noradrenaline and ATP and calcium regulating hormones, PGE2, PTH and calcitonin on bone blood flow and strontium clearance have been investigated in an experimental model in the rat. In order to proceed with this work smaller studies were undertaken to develop and validate the technique used to measure flow and clearance. These included; 1. validation of choice of cannulation site, 2. investigation of rat bone haematocrit, 3. determination of an appropriate withdrawal rate. Cannulation of the carotid artery and insertion of the cannula into the ventricle provides adequate mixing of the microspheres, withdrawal at the caudal artery (0.197ml/min) an adequate reference sample. The haematocrit work suggests that a correction factor may be required when using this procedure as the haematocrit of rat bone is consistently less than that of the caudal artery. However the results in this study are too variable to incorporate this finding in the bone blood flow and clearance work.