Segmental chloride transport in the Dahl-S rat kidney during L-arginine administration.

L-Arginine normalizes pressure natriuresis in Dahl salt-sensitive (DS) rats. The nephron segments responsible for improvement in sodium chloride handling during L-arginine administration are unknown. Micropuncture techniques were used to examine fluid and chloride transport along superficial nephron segments in DS rats maintained on an 8% sodium diet and given L-arginine or vehicle ip for 3 wk. Renal perfusion pressure in vehicle-treated DS rats was reduced to that of L-arginine-treated DS rats with an aortic snare. Dahl salt-resistant (DR) rats receiving vehicle were examined for comparison. In agreement with previous studies, urinary sodium chloride excretion was greater (P < 0.05) in L-arginine DS rats than in vehicle DS rats and not different from DR rats at equivalent renal perfusion pressures. Whole-kidney and single-nephron GFR were not different (P = not significant) among groups. Fractional proximal tubule chloride and fluid reabsorption was not different among groups. Fractional loop chloride reabsorption was greater in vehicle-treated DS rats than in DR rats (58.5 +/- 1.5 versus 46.6 +/- 1.7%; P < 0.05), confirming the enhanced chloride reabsorption at this location in DS rats previously reported. Fractional loop chloride reabsorption was identical in vehicle- and L-arginine-treated DS rats (58.4 +/- 1.4 versus 58.9 +/- 3.9%; P = not significant). Fractional loop fluid reabsorption was not different among groups. Fractional distal fluid and chloride reabsorption was not different between DS rat groups.(ABSTRACT TRUNCATED AT 250 WORDS)