Aging-associated increase in intestinal permeability to polyethylene glycol 900

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Abstract
Effect of aging on the intestinal permeability to medium size [3H]polyethylene glycol (PEG 900) was examinedin vivo by gavage andin vitro in intestinal everted sacs of rats ranging in age from 5 to 102 weeks. Rats were gavaged with PEG 900 solution and urinary recovery of PEG 900 was measured for 6 hr in order to assess its absorption. Young rats, 5–15 weeks of age, absorbed 1–1.3% of administered PEG 900. In contrast, rats 35–102 weeks of age absorbed 1.8–2.4% of administered PEG 900 (PP<0.05) in older rats (100 weeks) than young rats (9 1/2 weeks), while urinary excretion of PEG 900 following intravenous injection was the same in the two age groups. These studies indicate that aging rats have diminished capacity to exclude larger size molecules from penetrating the intestinal mucosa. The diminished barrier functions of the small intestine with aging may allow antigenic or mutagenic compounds to reach the systemic circulation.