Effect of aging on the hepatobiliary transport of dimeric immunoglobulin A in the male Fischer rat.

Recent studies have suggested that the hepatobiliary transport of serum dimeric immunoglobulin A constitutes an important secretory route for this ligand. However, the information that is currently available has been accumulated from studies in young animals or in patients with liver disease. Aging is known to result in (a) reduced hepatobiliary function(s), (b) an increased incidence of gastrointestinal infectious diseases, and (c) a marked decline in the immune response. We evaluated the effect of aging on the in vivo hepatic capacity to transport dimeric immunoglobulin A from blood to bile. Young adult rats (3-4 mo) secreted 125I-labeled dimeric immunoglobulin A into the bile at a rate sixfold greater than that measured in either mature (12 mo) or senescent (24-25 mo) animals. This age-related decline appears to be relatively independent of bile flow and bile acid secretion. Quantitative light and electron microscopic autoradiographic evidence suggests that aging may impair the rate at which this ligand is translocated across the hepatocytes to the bile canaliculi.