Glucose absorption by in vitro perfused colon of the fetal rat

The anatomic configuration of fetal rat colon resembles that of the small bowel. Accordingly, glucose and amino acid absorption were measured in order to see whether the fetal rat colon resembled the small bowel functionally. In vitro luminal perfusion of the fetal rat colon at 20 days of gestation was employed to measure the rate of glucose and L-alanine absorption and the unidirectional flux rates of 3-O-methylglucose (3-O-MG). The colon was mounted between pipettes in a heated oxygenated bath and perfused with the solute to be studied dissolved in buffered physiological solution and polyethylene glycol with average molecular weight of 4,000 (PEG) as a nonabsorbable marker substance. The PEG was not transported and did not diffuse across fetal colon. Scanning and transmission electron microscopy of perfused and control colon showed the presence of villi and the preservation of mucosal anatomy during perfusion. Glucose was absorbed at 173 +/- 16 mumol . h-1 . g-1 (8) and absorption was abolished in Na-free solution. 3-O-MG flux was 40 +/- 7 mumol . h-1 . g-1 (8) from lumen to bath and 7 +/- 1 mumol . h-1 . g-1 (8) from bath to lumen. L-Alanine flux was 130 +/- 15 mumol . h-1 . g-1 (8) from lumen to bath and 18 +/- 4 mumol . h-1 . g-1 (5) from bath to lumen, and the lumen-to-bath flux was only partially abolished by Na-free solutions.