Inhibition by potassium ion of the intestinal absorption of glucose

Abstract

A study has been made of the effect of potassium ions on the absorption of glucose by the small intestine of the rat, with the in vivo technique of Sols and Ponz. The concentrations tested were of 20, 40, 75 and 154 mM glucose, and 6, 15, 30, 60 and 77 m. eq./l. of potassium ion. On each animal four successive absorptions were carried out, of thirty minutes each: the first and third with a solution of pure glucose; the second and fourth with a solution of glucose plus potassium. The results are expressed as /xM of sugar absorbed per cm of length of intestine, and the % of inhibition obtained in the following successive absorptions with respect to the first, considered as normal in all the experiments.

An inhibition has been obtained which varies, although not lineally, with the concentration of cation. The inhibitions found are statistically significant for any concentration of potassium (Table I), independently of the concentrations of glucose tested (Table II). For 15 m. eq./l. of K+, the inhibition is reduced (5 % + 0.8), but no increase in the intensity of absorption ever appears, as been found in vitro by Riklis and Quastel.

The inhibitions cannot be attributed to an osmotic effect resulting from the increase in concentration by the dissolution of the ions, as an equal concentration of sodium ions provokes a contrary effect. The addition of sodium to pure solutions of glucose increases the absorption in a similar proportion % to that of the inhibition produced on the same by its equivalent of potassium (Table VI).

The washing of the intestinal loop with an isotonic solution of C1K produces an inhibition of 14 % (Table IV), and intensifies the effects produced by the presence of the potassium in the same loop as the sugar (Table VII).

For concentrations equal to, or less than 60 m. eq./l. of K+, the inhibition is made reversible by simply washing the loop, before the following absorption, with an isotonic solution of CINa. Higher concentrations (77-154 m. eq./l.) render the inhibiting effect persistent, perhaps on account of a strong toxic action which shows itself even in those experiments in which the potassium is found in a different loop from that which absorbs the glucose (Table VII). In these latters conditions there is no significant inhibition below 60 m. eq./l.

The inhibiting effect of the potassium is neutralized by the presence in the same loop of the equivalent quantity of sodium ions (Table V).

The results obtained suggest a double effect of the potassium ions on the intestinal absorption in vivo of glucose: a general one, only appreciable for higt concentrations of cation, and caused by a toxic action on the cellular physiology, and a local one, which seems to depend on the concentration of sodium ions present.