Effect of Renal Nerve Stimulation on NaCl and H2O Transport in Henle's Loop of the Rat

To assess the effect of renal nerve stimulation on sodium, chloride, and water transport in the loop of Henle, experiments were performed in anesthetized hydropenic and isotonic saline volume-expanded rats using renal clearance and Henle's loop microperfusion techniques (end-proximal convoluted tubule perfusion site, early distal convoluted tubule collection site). As compared with the control period values, low-frequency (less than 1.0 Hz) renal nerve stimulation decreased absolute and fractional urinary flow rate and sodium and chloride excretion without affecting mean arterial pressure, glomerular filtration rate, renal blood flow, or renal vascular resistance. In the loop of Henle, the absorptive transport of water was not affected, whereas the absorptive transport of sodium and chloride was increased in both hydropenic (Na 111 +/- 49 peq/min) and isotonic saline volume-expanded rats (Na 154 +/- 69 peq/min, Cl 180 +/- 52 peq/min) during low-frequency renal nerve stimulation. Low-frequency renal nerve stimulation decreases urinary sodium and chloride excretion via a direct effect of increasing renal tubular sodium and chloride reabsorption. In addition to the established effect of increasing proximal tubular sodium reabsorption, Henle's loop sodium and chloride absorption are also increased, supporting a physiological role for the adrenergic innervation of these structures.