Intravascular receptors and renal responses of monkey to volume expansion

Experiments were performed in anesthetized Macaca fascicularis monkeys to determine the effects of combined thoracic dorsal rhizotomy (C8-T7) and vagotomy-sinoaortic denervation on the renal responses to acute intravascular volume expansion. Expansion of the estimated blood volume by 15% with 6% dextran in isotonic saline produced attenuated diuretic and natriuretic responses in the denervated animals when compared with sham-operated controls. The times to peak diuresis and natriuresis after volume expansion also were significantly earlier in the denervated group. Although central venous pressure increased similarly in both groups, mean arterial pressure increased to a greater extent after volume expansion in the denervated group. As opposed to the previously reported failure of either denervation alone to attenuate the renal responses to hypervolemia in the monkey, our results suggest that these neural pathways may play a role in maintaining salt and water balance in this species. However, because of the possibility of functionally redundant afferent mechanisms, blunted renal responses to volume expansion in the primate can only be demonstrated after an extensive denervation.