Further Observations on the Relationship Between the Metabolism of Galactose and Glucose. ∗

Abstract

It is a striking fact that lactose is found in but one place in nature, in the mammary secretion, milk. More information may well be obtained about it and its products of hydrolysis, particularly the galactose moiety. Several investigators have found that tolerance for galactose is less than for a mixture of glucose and galactose. The evidence presented has been the decreased urinary excretion and the less striking change in the blood sugar when glucose accompanied the galactose. One objection to such observations, and a limitation to their interpretation, lies in the absence of knowledge of what changes in galactose concentration of the blood and urine are taking place.

A method for the estimation of galactose in blood and urine has been developed, 1 and applied in an effort to learn more of the relationship between the metabolism of glucose and galactose. Glucose injected simultaneously with galactose has increased the rate of removal of the latter from the blood, but the effect could be explained at least in large measure by the greater urinary excretion resulting. 2 Glucose has been found to have a very marked effect on the amount of galactose appearing in the blood stream when the 2 sugars were fed. 3 However, glucose had an analogous influence on the appearance in the blood xylose, a pentose sugar, and one between which and glucose no metabolic relationship has been shown. 4

A critical consideration of the data has not entirely ruled out the possibility that glucose has a more intimate connection with the metabolism of galactose, although the results as indicated above can be explained on other bases. Therefore it has seemed of interest to choose different experimental procedures, with the expectation that if the glucose and galactose were to enter the body by different channels, conjugated excretory effects and absorptive interrelationships would be obviated. Rabbits have been used. Experimental details have been described in earlier communications.