TAURINE STATUS IN CATS IS NOT MAINTAINED BY DIETARY CYSTEINESULFINIC ACID

Endogenous synthesis of taurine by cats is limited, Putative precursor s of taurine, cysteinesulfinic acid and cysteic acid, were fed to cats to determine whether they were utilized. Groups of five cats were dep leted of taurine by a resin (Colestipol(R)) diet, then given 6 dietary treatments containing (g/kg diet): 0.0, 0.4, or 0.8 taurine; or 0.98 or 1.96 cysteinesulfinic acid, or 0.4 taurine + 1.0 cysteic acid for 1 2 wk. Plasma and whole blood taurine concentrations and body weights w ere measured weekly, Concentration of taurine in semitendinosus muscle was measured initially, after 2 wk of taurine depletion (after resin- diet), and monthly thereafter. The resin diet decreased concentrations of taurine in plasma, whole blood, and muscle to 0.20, 0.49, and 0.37 of initial values, respectively. Cysteinesulfinic acid diets resulted in no significant (P > 0.05) increase in the concentration of taurine in plasma, whole blood, or muscle, and no increased excretion of cyst einesulfinate or taurine in urine or feces. Cats fed the diets contain ing 1.0 g cysteic acid + 0.4 g taurine, or 0.8 g taurine/kg diet had s imilar concentrations of taurine in plasma, whole blood, and muscle. A minotransferase activity for cysteinesulfinic acid in the liver and in testinal mucosa of cats and rats was higher than that for aspartic or cysteic acids, Transamination of dietary cysteinesulfinic acid to beta -sulfinylpyruvate (which spontaneously decomposes), rather than decarb oxylation is postulated as the basis for no detectable conversion to t aurine. In contrast, cysteic acid is reversibly transaminated to beta- sulfopyruvate which is stable and thereby is a precursor for taurine i n cats.