Intestinal absorption of two glucose analogues in rats of different ages

Intestinal absorption of nutrients and xenobiotics has been suggested to change during aging. Transport processes were examined using nonmetabolizable glucose analogues as markers in an in situ single pass intestinal perfusion procedure. Male Fischer 344 rats of 2, 4, 10, 16, and 27 months of age were used in this study. At least 7 rats were used per age group. Net active and passive transport were estimated using 0.85% NaCl solutions containing [ 14C]-3-O-methylglucose (3OMG) and [ 3H]-2-deoxy-D-glucose (2DG) and phenol red as a nonabsorbed volume marker. Rats were anesthetized and approximately 30 cm of jejunum was perfused for 30 min. Final glucose analogue concentrations were corrected for volume changes, and compared with initial concentrations. Changes in marker concentrations were normalized to the dry weight of the perfused intestinal segment. Concurrent exposure to both glucose analogues allowed simultaneous monitoring of active and passive components. Under these conditions, there was no significant change in the net transport of 2DG, a compound absorbed by nonspecific processes (range 17–33 μmoles/g/h). In the same animals, the rate of net 3OMG absorption, an actively transported compound, was generally an order of magnitude greater than 2DG. In addition, net 3OMG absorption was significantly ( p < .05) decreased in the 16- and 27-month-old rats (237 and 181 μmoles/g/h) compared with the 2-, 4- and 10-month-old animals (325, 364 and 398 μmoles/g/h, respectively). There appears to be a gradual decrease in net active transport of glucose with age. The mechanism responsible for this age-related change remains to be explained.