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 permeability to the inert polymer marker polyethylene glycol (PEG) with molecular 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 was collected for 24 hours to obtain the urinary recovery of the different PEG polymers as a measure of intestinal absorption. To study the intestinal permeability, segments from the proximal small intestine were incubated in diffusion chambers with the PEG mixture on the mucosal side, and samples were withdrawn from the serosal side for analysis. The urinary recovery for the PEGs increased (P < .01) while the tissue permeability decreased (P < .001) in the PCS group rats in comparison with Sham-operated rats. The increased absorption in vivo was caused neither 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. This discrepancy indicates that changes in permeability and absorption may 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.