A study of the vascular arrangement in the rat adrenal gland using non-radioactive microspheres

The intra-glandular vascular arrangement in the adrenal has been studied using non-radioactive microspheres injected by three different routes: in-vivo injection into the left ventricle under pentobarbital anesthesia, postmortem orthograde, and postmortem retrograde injection. The doses of microspheres were 10(5) (average size 24.7 micrometers), 10(6) (15.8 micrometers) and 10(7) (9.9 micrometers). The entrapment rate of microspheres by the medulla as compared with the whole gland was measured in the serially sectioned tissue (section thickness 60 micrometers). The entrapment rates of 25-micrometers microspheres differed between the orthograde and retrograde injections, while the entrapment rates for 15-micrometers microspheres were essentially similar irrespective of the route of injection. Our results support the conclusion from previous microangiographic studies that the adrenal cortex and medulla are supplied by different arteries but have a common venous outflow, and that direct communication between cortical and medullary sinusoids is not likely. The medullary blood flow per gram tissue weight is estimated to be larger than cortical blood flow.