N Premature infants have a high concentration of conjugated bilirubin in their blood, although they have a poor glucuronide conjugation of bilirubin.

Developmental changes in urinary coproporphyrin ratio in premature infants

Yusei Nakata 

 

Background

Premature infants have a high concentration of conjugated bilirubin in their blood, although they have a poor glucuronide conjugation of bilirubin. This may be due to developmental changes in the function of ATP‐binding cassette subfamily C member 2 (ABCC2), which is involved in the cellular export of conjugated bilirubin. In the present study, we examined the developmental changes in the UCP [I / (I+III)] (urinary coproporphyrin I / (urinary coproporphyrin I + urinary coproporphyrin III) ratio), a known biomarker for ABCC2 function, in premature infants.

Method

Twenty‐one premature infants born between 25 and 32 weeks of gestation were included in the study. Urine samples were collected within 24 hours of birth, and at 1 week and 3‐4 weeks after birth. The samples were analyzed by high‐performance liquid chromatography to calculate UCP [I / (I+III)] in order to examine its association with postnatal age and corrected gestational age. Subjects were excluded if they had liver dysfunction, cholestasis, urinary tract infection, or chromosomal abnormalities.

Results

The average UCP [I / (I+III)] within 24 hours of birth, at 1 week, and at 3‐4 weeks after birth was 0.84, 0.61, and 0.65, respectively. The UCP [I / (I+III)] within 24 hours of birth was significantly higher than that measured at 1 week or 3‐4 weeks after birth. There was no significant correlation between UCP [I / (I+III)] and the corrected gestational age.

Conclusion

The UCP [I / (I+III)] was higher within 24 hours of birth. It decreased 1 week after birth and remained low without any significant changes for up to 4 weeks after birth.