Sulfobromophthalein sodium (BSP) conjugation and excretion in neonatal guinea pigs

Abstract

The proportion of injected unconjugated and conjugated S35-labeled BSP excreted into bile in 1 hr was determined in neonatal guinea pigs at various ages after birth, and compared to values obtained in adult animals receiving comparable weight-adjusted doses of the respective compounds. Injected conjugated BSP was excreted into bile as readily in newborn guinea pigs 1 day of age, and older, as in adult animals. By contrast unconjugated BSP was excreted into bile more slowly in 1-day-old guinea pigs than in adults. Excretion of administered unconjugated dye reached adult levels between 5 and 12 days postpartum. Since unconjugated BSP is taken up by the liver at least as readily as conjugated BSP, if not more so, these data indicate that impaired conjugation of dye accounts for slower BSP delivery into bile in neonatal guinea pigs. This conclusion is further supported by the observations that both the enzyme that catalyzes BSP conjugation and glutathione, which is the substrate for conjugation, are decreased in livers of newborn animals.