Renal nerves and the natriuresis following unilateral renal exclusion in the rat.

Both acute unilateral nephrectomy (AUN) and acute ureteral pressure elevation (UPE) stimulate sodium excretion (UNaV) from the contralateral kidney, a response which in each case is interrupted by prior denervation of either kidney. Yet the natriuresis after AUN is known to be related to an increase in the plasma concentration of a gamma-melanocyte stimulating hormone (gamma-MSH)-like peptide. In anesthetized rats, sham AUN had no effect on contralateral UNaV, and plasma immunoreactive (IR) gamma-MSH concentration was 10.6 +/- 3.0 (SD) fmol/ml. In rats with intact renal innervation, UNaV more than doubled after AUN (P less than 0.001), and IR-gamma-MSH was increased to 14.9 +/- 4.6 fmol/ml (P less than 0.025). Unilateral renal denervation led to the expected increase in ipsilateral and decrease in contralateral UNaV, and neither sham AUN nor AUN of the denervated of innervated kidney influenced UNaV. In all three of these groups, IR-gamma-MSH concentration was reduced below the sham or post-AUN values seen in rats with innervated kidneys, to 4.9 +/- 3.3, 3.8 +/- 3.4, and 2.8 +/- 3.5 fmol/ml, respectively (P less than 0.001 for all). These results suggested that removal of renal afferent nerve input by renal denervation lowered basal IR-gamma-MSH activity and prevented the stimulated level normally seen after AUN. To examine the effect of stimulating afferent renal nerve activity, we carried out UPE, a maneuver known to increase ipsilateral afferent renal nerve traffic through activation of renal mechanoreceptors, as well as cause a natriuresis from the contralateral kidney.(ABSTRACT TRUNCATED AT 250 WORDS)