Renal nerves and initial excretory responses to recumbency: a species comparison

Experiments were performed in anesthetized Macaca fascicularis monkeys and mongrel dogs to determine if there are species differences concerning the involvement of the renal nerves in mediating the initial renal effects occurring with the assumption of recumbency. All animals underwent acute unilateral renal denervation with the contralateral kidney serving as the innervated control. Renal perfusion pressure was controlled throughout each experiment. Control measurements were made with all animals tilted head up 45 degrees, and recumbent measurements were made 5-15 min after the animals were lowered to 0 degree. In the monkeys, similar increases in urine flow, absolute and fractional sodium excretion, and creatinine and p-aminohippurate clearances occurred in both the innervated and denervated kidneys during recumbency. In contrast, in the dogs, renal denervation abolished these responses in that increases in these parameters occurred in the innervated kidneys only. These results demonstrate that the initial diuresis and natriuresis of recumbency are dependent on the presence of the renal nerves in the dog but not in the monkey.