Inhibition of the selective absorption of sugars by thorium ion

Abstract

The object of study, using the Sols and Ponz technique of successive absorptions, is the action of the thorium ion (chloride) on the intestinal absorption of sugars in the rat. Four successive absorptions are carried out on each animal, lasting thirty (with hexoses) or sixty (with 1-arabinose) minutes. The Solutions of sugars were 0.3 M.

With the hexoses (d-glucose, d-galactose and d-fructose), the first and third absorptions are carried out without an inhibitor, while in the second and fourth the same solution of sugar contains the thorium ion in the concentration desired. For the 1-arabinose, the thorium ion is present only in the third absorptions.

The intestinal absorption of d-glucose, d-galactose and d-fructose (tables I, II and III), is clearly inhibited (25-40 %) by the thorium ion 5 x 10-4 M, while it has no effect on the absorption of 1-arabinose (table IV).

The inhibiting effect of the thorium is not nonspecific. Experiments with two intestine handlers revealed that its action is local on the absorbing epithelium. The thorium ion forms stable complexes in the membrane, from which complexes it is not separated by a simple washing with saline solution, but a treatment with a solution of EDTA of 1 % can free them (table VI), thereby restoring the absorbing capacity of the intestine.

The effect of the thorium ion is fairly similar to that described for the uranyl ion (5).