INHIBITION OF SULFATE EXCRETION BY (AMINOOXY)ACETATE INDUCED STIMULATION OF TAURINE EXCRETION IN RATS

L-Cysteine is mainly metabolized to sulfate and taurine through cystei nesulfinate pathway. Alternatively, sulfate is formed in rat liver mit ochondria via 3-mercaptopyruvate pathway. Intraperitoneal administrati on of 5 mmol of L-cysteine per kg of body weight resulted in the incre ase in sulfate and taurine (plus hypotaurine) excretion in the 24-h ur ine, which corresponded to 45.3 and 29.3%, respectively, of L-cysteine administered. Subcutaneous injection of (aminooxy)acetate, a potent i nhibitor of transaminases, together with L-cysteine halved the sulfate excretion and doubled the taurine excretion. In vitro sulfate formati on from L-cysteine and from L-cysteinesulfinate in rat liver mitochond ria was inhibited by (aminooxy)acetate. The sulfate-forming activity o f liver mitochondria obtained from rats injected with (aminooxy) aceta te was also inhibited. These results indicate that the transamination reaction is crucial in sulfate formation and in the regulation of sulf ur metabolism. Sulfur equilibrium in mammals was discussed.