Blood flow to the adrenal gland of the rat: its distribution between the cortex and the medulla before and after haemorrhage.

This study has investigated the flow of blood to the adrenal gland of the anaesthetised rat under basal conditions and after the induction of haemorrhagic hypotension. By combining the use of radioactive microspheres with subsequent serial sectioning we have been able not only to assess total adrenal blood flow but also to determine its distribution within the gland. In normal anaesthetised rats approximately 7.4% of the adrenal blood flow passes directly to the medulla, the remainder being distributed to the cortex. This proportional flow is also observed immediately after withdrawal of sufficient venous blood to cause a 32% reduction in systolic blood pressure. However, the latter procedure results in a 52% increase in the total blood flow to the gland despite the associated fall in cardiac output.