Bile salt metabolism in the human premature infant. Preliminary observations of pool size and synthesis rate following prenatal administration of dexamethasone and phenobarbital.

Bile salt synthesis and bile salt pool size were determined by isotope dilution in two groups of healthy premature infants, utilizing nonradioactive deuterium-labeled bile salts. All 9 infants were between 32 and 36 weeks of gestation; however, in one group (4 infants), the mothers had received either dexamethasone or phenobarbital prior to delivery. The total bile salt pool averaged 20 mg for the infants of untreated mothers and 79 mg for the infants of treated mothers; similarly, the bile salt synthesis of 8 mg per day in the untreated group was increased to 27 mg per day for the treated group. Expressed per sq m of body surface, the cholic acid pool for the treated group was 321 mg per sq m, and the cholic acid synthesis rate equaled 98 mg per sq m per day; values equal to those for full term infants and nearly 4 times those for the untreated prematures. The intraduodenal bile salt concentrations obtained during meals were also low in the untreated group, equaling 1.2 mM as compared to 5.3 mM for the treated group. The reductions of bile salt pool size, synthesis, and intestinal concentration establish that the functional maturity of the liver, and possibly the gastrointestinal tract, is reduced in premature infants. The results further suggest that this maturity may be dramatically influenced by medications administered to the mother prior to delivery.