Renal nerves in renal adaptation to dietary sodium restriction

To assess the physiologic importance of the renal nerves in the renal mechanisms for the maintenance of body sodium balance, renal adaptation to normal and low sodium diet was evaluated in conscious Sprague-Dawley male rats before and 8 days after recovery from bilateral surgical-pharmacological renal denervation. Renal denervation was confirmed in every rat at the end of the study by absence of renal vasoconstriction to splanchnic nerve stimulation and loss of renal tissue norepinephrine content. Daily sodium balance, defined as the difference between dietary sodium intake and urinary sodium excretion, was positive with the normal sodium diet before and after bilateral renal denervation. Prior to bilateral renal denervation, changing to the low sodium diet was associated with a diminishingly negative sodium balance for 3 days that became progressively positive thereafter. After bilateral renal denervation, changing to the low sodium diet was associated with a continuous and progressively negative sodium balance. We conclude that intact renal innervation is required for normal renal sodium conservation and maintenance of body sodium balance during dietary sodium restriction.