Immaturity of the biliary excretory system predisposes neonates to intrahepatic cholestasis

Current research in necrotizing enterocolitis

Despite decades of research on necrotizing enterocolitis, we still do not fully understand the pathogenesis of the disease, how to prevent or how to treat the disease. However, as a result of recent significant advances in the microbiology, molecular biology, and cell biology of the intestine of premature infants and infants with necrotizing enterocolitis, there is some hope that research into this devastating disease will yield some important translation into improved outcomes.

Management of cholestasis in infants with very low birth weight

Infants with very low birth weight (VLBW) are at increased risk of cholestasis when compared with older infants and children. Factors associated with this increased risk of cholestasis include immaturity of the biliary excretory system, a diminished immune response to sepsis, an increased incidence of necrotizing enterocolitis and short bowel syndrome, as well as an increased exposure to parenteral nutrition (PN). The current literature on cholestasis in VLBW infants and the factors that mediate the initiation and progression of cholestatic liver damage is reviewed. A protocol for managing infants with cholestatic jaundice is presented, and a case report is included that shows use of the protocol to normalize the bilirubin in a VLBW infant with severe cholestatic jaundice.

Bile acid conjugation pattern in the isolated perfused rat liver during infusion of an amino acid formulation

The influence of the taurine-containing amino acid mixture Trophamine on the pattern of bile acid conjugation was examined in the isolated perfused rat liver using cholic acid as the bile acid substrate. In all experiments, greater than 97% of the cholic acid appearing in bile was conjugated with taurine or glycine. The pattern of taurine and glycine bile acid conjugation, however, was dependent on the availability of taurine in the perfusate medium. Thus, in the absence of Trophamine infusion, the percentage of cholic acid conjugated with taurine (ie, taurocholate) declined throughout the course of the cholic acid infusion. Trophamine infusion increased the ratio of biliary taurocholate/glycocholate by 4.5-fold over that observed in the absence of the amino acid infusion. Increasing the amount of taurine in Trophamine by 2- or 5-fold resulted in a 1.8- and 4.3-fold increase, respectively, in the taurocholate/glycocholate ratio over that observed during the Trophamine infusion. Infusion of taurine alone, at an equimolar concentration of taurine as that in Trophamine, resulted in a similar taurocholate/glycocholate ratio as that observed during the Trophamine infusion. These data indicate that taurine availability, even in the presence of high concentrations of glycine and other amino acids in Trophamine, appears to be the most important factor in determining the pattern of bile acid conjugation in the isolated perfused rat liver.

Inhibition of bile flow in the isolated perfused rat liver by a synthetic parenteral amino acid mixture: associated net amino acid fluxes

To identify a role for amino acids in cholestasis associated with total parenteral nutrition, we measured bile formation by the isolated perfused rat liver in the presence and absence of added amino acids. All livers were infused constantly with sodium [14C]taurocholate (0.28 mumoles per min) for 90 min. At 40 min, a primed-constant infusion of a synthetic L-amino acid mixture (121 + 19.3 mumoles of N per min) was administered for an additional 50 min. Mean bile flow rates during the amino acid infusion were reduced from 15.4 microliter per min per 10 gm liver weight to 10.4 microliter per min per 10 gm (p less than 0.005). There was no significant change during saline infusion of control livers, and there was no significant difference in perfusate osmolalities in the two groups. Although biliary recovery of infused taurocholate was slightly lower in the experimental perfusions than in controls (95.3% vs. 101.7%, p less than 0.05), there was no significant reduction in taurocholate excretion rate during the infusion in either group. Bile flow changes were related to ambient concentrations and net fluxes of individual amino acids in the perfusate. Of the 14 infused amino acids, glycine and arginine achieved levels greater than 3 times greater than reported physiological postprandial portal venous concentrations in the rat, and together constituted about 25% of the 90-min perfusate amino acids (8.3 mM). The highest net hepatic uptake was for glycine (125 mumoles per hr per 10 gm), which was almost 50% of its infusion rate.(ABSTRACT TRUNCATED AT 250 WORDS)