Decreased renal blood flow during mild, dynamic exercise in the baboon

Six chair-restrained, male baboons (Papio cynocephalus, 13 to 16 kg) were operantly conditioned with food reinforcement to perform four minutes of dynamic leg exercise in response to a visual cue. The exercise apparatus was a braked, drum-like wheel positioned beneath the seated animal. Following training, an electromagnetic flow transducer and an hydraulic occluder were placed around the left renal artery to record Renal Blood Flow (RBF). Special care was taken to minimize damage to renal nerves. An arterial catheter was chronically implanted to measure Blood Pressure (BP) and Heart Rate (HR). Oxygen consumption (V(O₂)) was determined with an uncompensated flow-through system. By the last minute of exercise, RBF decreased 20 + 3(SE)% with respect to rest despite a 21 ± 2% rise in BP. HR increased 41 ± 5%. V(O₂) rose from resting levels of 6.2 ± 0.6 to 20.2 ± 1.4 cc O₂/kg/min. In four similarly trained and equipped animals an additional flow transducer and occluder were placed on the right renal artery. All visible nerves to the right kidney had been cut and the artery, vein, and ureter stripped. During exercise the decrease in RBF in the denervated kidney was markedly attenuated (60 to 100%) compared with that observed in the innervated kidney. The authors conclude that the baboon, like man, but apparently unlike the dog, exhibits renal vasoconstriction during short mild exercise. This response is primarily mediated by neural mechanisms.