Renal excretory responses to saline load in the taurine-depleted and the taurine-supplemented rat

Taurine is found in high concentrations in mammalian cells. Despite recognition of its role as an organic osmolyte in the kidney, information regarding its effects on renal fluid and electrolyte excretion is sparse. Therefore, the objective of the first series of experiments was to determine the effects of taurine depletion on renal excretory responses to a saline load. To induce taurine depletion, male Wistar-Kyoto (WKY) rats were created with tap water containing 3% β-alanine for 3 weeks. Taurine depletion reduced the initial rates of fluid and sodium excretion after an intravenous saline load. This effect was attributed to taurine depletion since maintenance of the raurine depleted rats on tap water for 2 days to remove the effects of β-alanine yielded the same pattern as the taurine-depleted rats exposed to p alanine at the time of the experiment. Nonetheless, rats exposed to short-term p alanine treatment, which has no influence on kidney taurine content, demonstrated a larger (~ 25%) natriuretic but not diuretic response to the isotonic saline load than either the control or taurine-depleted rats. These data suggest that p alanine-induced inhibition of tubular reabsorption of taurine may result in subsequent excretion of taurine with attendant natriuresis early in the course of β-alanine treatment. We also tested the hypothesis that taurine potentiates the renal excretory responses to an isotonic saline load in WKY rats. Inclusion of taurine in the infusate significantly increased natriuresis and diuresis after a saline load. This effect was greater in animals fed a basal than a high NaCl diet. Our data support a role for taurine as a natriuretic and diuretic agent.