Intestinal absorption of sorbitol and effects of its acute administration on glucose homeostasis in normal rats.

Intestinal absorption of sorbitol was studied in a duodeno-jejunal loop of anaesthetized rats. The acute effects of exogenous sorbitol on glucose homeostasis were also evaluated in male and female rats. In the presence of lumen concentrations of sorbitol ranging from 1 microM to 200 mM, a fairly constant low percentage (about 12%) of the loop's contents was absorbed after 30 min. This amount increased only slightly with time, but this was not due to sorbitol accumulation in the mucosal layer of the loop. 3-O-methylglucose was absorbed much more quickly than sorbitol, but did not interfere with sorbitol absorption. The latter was not impaired by omission of lumen sodium ions nor by phloridzin, both of which inhibited 3-O-methylglucose absorption. Gastric administration of sorbitol did not affect plasma glucose or insulin levels. Glucose or sucrose administration caused a similar rise in plasma glucose, but the increase in plasma insulin levels was larger after glucose than after sucrose administration. Intravenous administration of sorbitol slightly increased plasma glucose and insulin levels. These changes were, however, considerably smaller than those occurring after glucose administration. In the normal rat, intestinal absorption of sorbitol is passive and proceeds at a low rate. Acute oral administration of sorbitol does not affect glucose homeostasis, which is only slightly disturbed by a large intravenous load of sorbitol.