Blood mobilization by regional vascular beds during cerebral ischemic pressor response in rabbits.

The mobilization of blood volume from regional vascular beds during cerebral ischemic pressor response was studied in anesthetized rabbits. The visceral beds of the kidney, jejunum, and liver served as volume reservoirs from which blood was mobilized during cerebral ischemia. The renal bed gave the largest volume decrease, from 24 to 13%. The magnitude of weight change in the renal and intestinal regions varied in parallel to the volemic state of the animal. Superimposition of pressure oscillation on the systemic pressor response was created by progressive restriction of the blood supply to the brain. Regional tissue weights also oscillated with a period equal to that seen in arterial pressure but almost 180 degrees out of phase. Such variations gave evidence of active venoconstriction in the reservoir response of all regional beds except the hind paw. The responses noted in the hind paw were passive except during complete restriction of the blood flow to the brain. Autoregulation of skeletal muscle and especially liver volume was present with moderate elevations in systemic arterial pressure.