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 re cognition of its role as an organic osmolyte in the kidney, informatio n regarding its effects on renal fluid and electrolyte excretion is sp arse. Therefore, the objective of the first series of experiments was to determine the effects of taurine depletion on renal excretory respo nses to a saline load. To induce taurine depletion, male Wistar-Kyoto (WKY) rats were treated with tap water containing 3% beta-alanine for 3 weeks. Taurine depletion reduced the initial rates of fluid and sodi um excretion after an intravenous saline load. This effect was attribu ted to taurine depletion since maintenance of the taurine-depleted rat s on tap water for 2 days to remove the effects of beta-alanine yielde d the same pattern as die taurine-depleted rats exposed to beta-alanin e at the time of the experiment. Nonetheless, rats exposed to short-te rm beta-alanine treatment, which has no influence on kidney taurine co ntent, demonstrated a larger (similar to 25%) natriuretic but not diur etic response to the isotonic saline load than either the control or t aurine-depleted rats. These data suggest that beta-alanine-induced inh ibition of tubular reabsorption of taurine may result in subsequent ex cretion of taurine with attendant natriuresis early in the course of b eta-alanine treatment. We also tested the hypothesis that taurine pote ntiates the renal excretory responses to an isotonic saline load in WK Y rats. Inclusion of taurine in the infusate significantly increased n atriuresis and diuresis after a saline load. This effect was greater i n animals fed a basal than a high NaCl diet. Our data support a role f or taurine as a natriuretic and diuretic agent. (C) 1997 Elsevier Scie nce Inc.