SMALL-INTESTINAL ABSORPTION OF POLYETHYLENE-GLYCOL 400 TO 1,000 IN THE PORTACAVAL SHUNTED RAT

Functional changes of the intestinal barrier that may occur after the creation of a portacaval shunt (PCS) were investigated, After chronic PCS in the rat, the intestinal absorption of and the jejunal permeabil ity to the inert polymer marker polyethylene glycol (PEG) with molecul ar weight (Mw) ranging from 400 to 1,000 g/mol were investigated, The PEG mixture was orally fed to PCS and sham-operated rats, and urine wa s collected for 24 hours to obtain the urinary recovery of the differe nt PEG polymers as a measure of intestinal absorption To study the int estinal permeability, segments from the proximal small intestine were incubated in diffusion chambers with the PEG mixture on the mucosal si de, and samples were withdrawn hom the serosal side for analysis, The urinary recovery for the PEGs increased (P < .01) while the tissue per meability decreased (P < .001) in the PCS group rats in comparison wit h Sham-operated rats, The increased absorption in vivo was caused neit her by altered renal clearance, nor by changed portal blood pressure. The decreased jejunal permeability in the PCS rats could be explained by a reduction of the mucosal area by shortening of the microvilli. Th is discrepancy indicates that changes in permeability and absorption m ay not be parallel during PCS. It is possible that these changes also may be affected by nutritional factors, drug therapy, as well as toxic substances.