The distribution of cardiac output in the anaesthetized spontaneously hypertensive rat.

1. Radioactive 15 micrometer and 50 micrometer diameter microspheres were used to determine cardiac output, its regional distribution and tissue blood flow in adult normotensive Wistar and Okamoto spontaneously hypertensive rats. 2. Cardiac output in the spontaneously hypertensive rats was the same as in Wistar normotensive rats, but its distribution in the hypertensive rats appeared to differ: there was a significant increase in the proportion of microspheres trapped in the liver whereas fewer were found in the gastrointestinal tract. This indicates that a greater fraction of the cardiac output passes along the hepatic artery and less through the splanchnic bed. 3. Blood flow in skin and skeletal muscle in spontaneously hypertensive rats was approximately 50% of that in Wistar normotensive rats.