COMPARATIVE TRYPTOPHAN METABOLISM IN CATS AND RATS - DIFFERENCES IN ADAPTATION OF TRYPTOPHAN OXYGENASE AND IN VIVO METABOLISM OF TRYPTOPHAN, KYNURENINE AND HYDROXYKYNURENINE

1. 1. Comparative studies of tryptophan metabolism in cats and rats showed that tryptophan oxygenase was not induced by cortisol administration in cats, but was readily induced in rats. 2. 2. Induction of this enzyme by tryptophan was observed in cats but the response was less than in rats. 3. 3. Following oral loading doses of tryptophan, l-kynurenine or 3-hydroxy-dl-kynurenine, urinary excretion of metabolites was much greater in rats than in cats. 4. 4. Differences were also found in the excretion of sulfate and glucuronide conjugates of hydroxykynurenine. 5. 5. The unusual metabolism of tryptophan in cats was discussed in relation to previous enzyme studies and the unusually low spontaneous incidence of bladder cancer in cats. © 1969.