Bile acid composition in neonatal life in rats.

Bile acid (BA) metabolism was studied in the intestine, liver and plasma of rats at 0-1 day (neonates); 14 days (preweaning); 22 days (weaning) and 60 days (young adults) of age, as well as in the maternal tissues. In the intestine, total BA content (mumol/100 g body weight) decreased during neonatal life and reached maternal levels at 60 days. In the liver, BA increased up to 14 days and then decreased at 22 and 60 days of age, but these concentrations were higher than those found in the neonate and the mother. The serum concentrations in 14- and 22-day-old rats were more than 30 times higher than in the newborns. At 60 days, serum BA content was still twice that of the mother. BA composition in the intestine and the liver showed a reduction in 12 alpha-hydroxylated BA associated with an increase in chenodeoxycholic acid and 6 beta-hydroxylated BA during neonatal life. These data indicate an increased synthesis of chenodeoxycholic and 6 beta-hydroxylated BA after birth. It further suggests a possible defect in excretory mechanisms in neonatal life.