Metabolism of sorbitol and glucose compared in normal and alloxan-diabetic rats.

The question of the extent to which compounds structurally related to glucose are glucogenic in the rat has been the subject of earlier studies. The metabolic fates of meso-inositol (l), n-gluconic acid (2), and n-galactose (3) have been investigated after administration of isotopically labeled preparations of these substances. The present report deals with an extension of this line of investigation in which n-sorbitol and n-glucose have been studied in experiments essentially paralleling those with gluconic acid. Sorbitol has been shown to be well utilized by a variety of species including man and dog (4), pigeon (5), mouse (6), rabbit (7), and rat (8, 9). When administered in limited doses, very little sorbitol is excreted (4, S), but when larger amounts are given up to 50 per cent may be lost in the urine (9). The injection of sorbitol into the fasted rat is followed by an increase in the quantity of glycogen in the liver (8, 9). Oral administration gave conflicting results, some workers finding (9, 10) and other workers failing to find (11, 8, 12) an increase in hepatic glycogen. The intraperitoneal injection of sorbitol into fasted rats resulted in a greater increase in liver glycogen and a lesser increase in muscle glycogen than was provoked by parallel glucose administration (13). From experiments in which sorbitol was perfused through the liver of the previously phlorhizinized dog, Embden and Griesbach (14) suggested that fructose rather than glucose might be the initial oxidation product of sorbitol, a view which has received some support elsewhere (8, 15, 16). The possible usefulness of sorbitol in the diet of diabetic patients suggested by Thannhauser and Meyer (4), precipitated a controversy in the clinical literature which has been adequately reviewed elsewhere (9, 12, 17). The present experiments were designed to study the fate of sorbitol as compared with glucose in the non-fasting normal rat and also to determine the effect of alloxan diabetes upon sorbitol metabolism. Because of the known low rate of absorption of sorbitol from the intestinal tract (12) the test materials, uniformly labeled C”-glucose and C”-sorbitol derived from it, were administered by intraperitoneal injection. The use