Bilirubin-IXalpha and -IXbeta pigments, coproporphyrins and bile acids in meconium and stools from full-term and preterm neonates during the first month of life.
Individual bilirubin pigments in the excreta were quantitated by newly developed methods. In meconium, bilirubin-IXbeta predominated, whereas bilirubin-IXgamma and -IXdelta remained undetectable. The daily excretion of bilirubin-IXalpha plus -IXbeta was 0.03-1.00 and 0.04-2.00 micromoles kg(-1) of birthweight in preterm and full-term infants, respectively. The ratio of bilirubin-IXalpha to -IXbeta in meconium was 0.25 +/- 0.34, 0.32 +/- 0.30 and 0.46 +/- 0.55 in newborns of gestational ages below 30, from 31 to 36 and above 36 wk, respectively. The predominance of bilirubin-IXbeta disappeared within the first week in those with gestational age >31 wk but more slowly in the very preterm group. The ratio of monoconjugated to diconjugated bilirubin-IXalpha was 4 to 5 in full-term infants, whereas this ratio was only reached after 1 mo in preterm infants. The ratio of glucuronide or glucoside to xyloside varied widely, independent of gestational age. No correlation between faecal UCB-IXalpha and beta-glucuronidase was observed. The daily coproporphyrin excretion fell from a median of 500 microg on day 1 to below 20 microg from day 7 onwards; this decrease correlated with that of bilirubin-IXbeta. The daily 3alpha-hydroxylated bile acid loss in the excreta was two- to fivefold higher than in the adult; this, together with the higher neonatal serum levels (12-90 nmoles ml(-1)), indicates an immature intestinal reabsorption and an enhanced bile acid synthesis.


CONCLUSIONS
Both zinc coproporphyrin and bilirubin-lXbeta are characteristic compounds of human meconium, diconjugated bilirubin-IXalpha is low or absent in meconium of very preterm infants, and faecal and serum bile acids are high.
Department of Paediatrics, University Hospital Gasthuisberg, Leuven, Belgium.
S
S
Aziz
P
P
Kotal
P
P
Leroy
R
R
Servaes
E
E
Eggermont
J
J
Fevery
D001647:Bile Acids and Salts / Q000032:analysis*; D001663:Bilirubin / Q000032:analysis*; D003306:Coproporphyrins / Q000032:analysis*; D005243:Feces / Q000737:chemistry* / Q000201:enzymology; D005865:Gestational Age; D005966:Glucuronidase / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn / Q000502:physiology*; D007234:Infant, Premature / Q000502:physiology*; D008470:Meconium / Q000737:chemistry*
D001647:Bile Acids and Salts; D003306:Coproporphyrins; C031467:coproporphyrin I; D005966:Glucuronidase; D001663:Bilirubin