Absorption Rates of Galactose and Mannose. ∗

Abstract

The absorption rates of galactose and mannose were studied in rats and dogs using one hour as the absorption period. The rats were not fed during the 48 hours before being used but water was given as usual. One gram (2 cc. of a 50% sol.) of the sugar was given by stomach tube. Animals were killed by a blow on the head after which a ligature was tightly tied about the neck to prevent loss of sugar by mouth. The abdomen was then opened and ligatures placed about the oesophagus and lower end of ileum. This portion of the gastrointestinal tract was removed and the unabsorbed sugar washed out with warm water for quantity determinations.

In using closed loops of ileum in dogs 2 gm. of the sugar were given (10 cc. of a 20% sol. introduced by needle and syringe). At the end of an hour the content was aspirated and the loop washed by injecting warm physiological salt solution and aspirating. More complete description of these procedures has been published. 1

Sugars of definite rotation (d-galactose + 80.5°, d-mannose + 14.250°) were used and concentrations made by weight were checked by polariscope. Galactose determinations were made by the Shaffer-Hartman method for determining glucose, consequently 10% had to'be added to the findings to approximate the actual amount of galactose present. This method can not be used with any degree of accuracy for mannose estimations. A satisfactory method consists in reducing Benedict's qualitative solution and then plating the copper out and weighing the copper electrodes. 2

The results are shown in Table 1. While there is some difference in the comparative rates at which these 2 sugars were taken up by dogs and rats, the findings would seem to justify the conclusion that galactose is absorbed approximately twice as fast as mannose.