Renal nerves and renal responses to volume expansion in conscious monkeys

Experiments were performed in conscious macaque monkeys to determine the effect of renal denervation on the diuresis and natriuresis of blood volume expansion. When the kidneys were innervated, expansion of estimated blood volume by 20% with 3% dextran in isotonic saline caused increases in urine flow (V̇), from 0.28 ± 0.07 ml/min to a peak response of 1.08 ± 0.20 ml/min, absolute sodium excretion (U(Na)V̇), from 30.0 ± 11.2 to 99.8 ± 11.7 μeq/min, and fractional sodium excretion (FE(Na⁺)), from 1.24 ± 0.51 to 3.19 ± 0.56%. The animals then underwent bilateral renal denervation and were volume expanded a second time 6-13 days postdenervation. Under this condition, V̇ increased from 0.32 ± 0.05 to 0.64 ± 0.08 ml/min, U(Na)V̇, from 22.2 ± 4.6 to 46.2 ± 8.0 μeq/min, and FE(Na⁺), from 0.91 ± 0.26 to 1.92 ± 0.41%, these increases being significantly less than when the kidneys were innervated. These results demonstrate that the renal nerves play an important role in the nonhuman primate in mediating increases in renal excretion during hypervolemia.