[Changes in opposite directions of tryptophanpyrrolase and 3-OH-anthranilic oxidase after a loading dose of tryptophan].

A loading dose of tryptophan induces a marked increase of tryptophan-pyrrolase (substrate induction) and a decrease of 3-OH-anthranilic-oxidase values in rat liver; in the kidneys of the same experimental animals the 3-OH-anthranilic-oxydase is instead unchanged. In other experimental conditions (surrenectomized or pyridoxine depleted rats, with or without tryptophan loading; with prednisolone loading) a more or less important substrate induction is always reported, whereas no variation occurs in the values of 3-OH-anthranilic-oxydase. These data are not sufficient to state whether there is a connection between the opposite responses of the two enzymatic activities obtained after tryptophan loading in rat liver homogenate. On the other hand, it should be kept in mind that they do not represent the overall effect induced by the aminoacid loading, but refer only to one moment of the action exerted by the loading itself. In order to acquire a thorough knowledge of the observations made so far and to formulate some assumptions which may be helpful for the interpretation of the relevant mechanisms, it is necessary to investigate the kinetics of both enzymes, and to study their regulatory mechanisms in particular after tryptophan loading.