Abstract

The purpose of this investigation was to characterize the development of hepatic excretory function in rats. Cumulative (40 min) intestinal ouabain content was lower and plasma ouabain concentrations were higher in 15-day-old rats than in 21-, 25-, 35- and 45-day-old animals and reached adult levels when rats were 35 days old. Impaired transport of ouabain in rat neonates correlated to low initial ouabain concentration in liver, which suggested that the inability of young rats to accumulate ouabain in liver may be the most important determinant for functional insufficiency. Bile duct ligation and bile salt infusion, treatments that primarily depress and enhance (respectively) excretion of sulfobromophthalein from liver into bile, markedly altered the disappearance of sulfobromophthalein from plasma of adult rats but did not appreciably affect sulfobromophthalein disappearance from blood of 15-day-old rats. The effect of bile duct ligation on ouabain transport in 15-day-old rats was also not as dramatic as the effect produced in adult rats. Hepatic uptake is rapid in adult rats and overall excretion is limited by a slower rate of transport from liver into bile. The lower rate of uptake in 15-day-old rats may limit overall transport function in young animals.