The Substitution of Taurine for Cystine in the Diet of Mice

Abstract

There is no doubt that the Taurine wbich is produced by animals, and whieh occurs in vertebrates chieflj' in the form of Taurocbolic acid, is ultimately derived from Cystine. The question whether animal tissues are able to accomplish tbe reversion of this transformation and convert Taurine into Cystine has not yet been directly investigated, although tbe indirect evidence constituted by.the fact that Taurine and Cystine pursue separate paths of metabolism in the body, would appear to indicate that Taurine is not capable of transformation into Cystine under normal dietary conditions (4, 5).The following experiments were undertaken witb tbe object of investigating thi'i queBtion.It has been shown by Osborne and Mendel (3) that the presence of Cystine in the diet is necessary for the growth of young animalB. This observation was confirmed, and the effect of added Cj'stlne in rendering the diet adequate for growth was compared witb tbe effect of an equivalent addition of Taurine.A number of mice of from four to five weeks of age were divided, without selection, into three sets. One set, fed upon a synthetic diet M'hich contained sufficient Cystine to permit growth (15 per cent. Casein) wa.s employed as a control. The mice in the other two sets were fed upon a Cystine-dcficient diet (9 per pent. Casein), to which Taurine aud Cystine were respectively added at various intervals.The diet adopted was one based upon that employed by Osborne and Mendel (3). These investigators used rats in tbeir experiments, however, and the dietary habits of mice differ sufiiciently from those of rats to render certain modifications ci^ential. It was found impossible to overcome the repugnance of the animals for the synthetic diet without cooking it, and this, in turn, involved modification «f some of the proportions of the constituents of the diet used by Osborne and Mendel. The compositions of the diets were as follow t