Regional distribution of blood flow during mild dynamic leg exercise in the baboon

Five chair-restrained baboons were trained with operant techniques and a food reward to perform dynamic leg exercise. Cardiac output and blood flows to most tissues were determined by radioactive microsphere distribution. After 2 min of exercise mean arterial blood pressure had increased by 11 ± 3% (SE), heart rate by 34 ± 7%, cardiac output by 50 ± 12%, and O₂ consumption by 157 ± 17%. The blood flow to exercising leg muscle increased by 585 ± 338% and to the myocardium by 35 ± 19%. Blood flow to torso and limb skin fell by 38 ± 4 and 38 ± 6%, respectively, and similar reductions occurred in adipose tissue blood flow. Nonworking skeletal muscle blood flow decreased by 30 ± 10%. Renal blood flow was lowered by 16 ± 2%. The lower visceral organs had more variable responses, but when grouped together total splanchnic blood flow fell by 21 ± 9%. Blood flow to the brain was unchanged with exercise, whereas spinal cord perfusion increased 23 ± 3%. Thus during short dynamic exercise baboons redistributed blood flow away from skin, fat, nonworking muscles, and visceral organs to supply the needs of exercising muscles. Our data suggest the baboon is a useful animal model for investigating vascular responses of tissues, such as torso skin, adipose, individual visceral organs, and the spinal cord, that cannot be examined in humans.