Galactose Mixture by Slices of the Active Mammary Gland in Vitro

SVANBERG [1930] investigated the possibility that a brei made of the lactating mammary gland might synthesize lactose from added glucose or a glucosegalactose mixture. In his experiments toluene was used as a preservative, and the reducing sugars were partitioned into disaccharide and monosaccharide fractions. With one doubtful exception, the results were negative. Michlin & Lewitow [1934] carried out similar experiments and claimed, on the basis of irregular changes in the total reduction of their solutions, to have demonstrated the synthesis of lactose from glucose and galactose mixtures. Grant [1935] determined the extent of lactose synthesis by slices of the active mammary gland immersed in oxygenated physiological salt solutions containing different hexoses. A quantitative micro-method was developed for the estimation of small amounts of lactose, using S. fragilis J6rg., as a biological reagent for this sugar. An increased synthesis of lactose was readily obtained with glucose as a substrate, while there was little evidence of such synthesis from fructose, mannose or galactose. In the present communication, the amounts of lactose formed in vitro, when glucose or galactose, respectively, is a substrate for slices of lactating tissue, are compared with those obtained from equivalent amounts of glucose-galactose mixtures. EXPERIMENTAL.