Serum diamine oxidase in the neonate

Serum diamine oxidase (DAO) activities were measured in 9 pregnant women and in 33 neonates during the 1st week of life. The radiometric method was used. Very high values were found in the mothers (mean +/- SE: 720 +/- 143 pmol ml-1 h-1). Neonates showed significantly elevated values (mean +/- SE: 178 +/- 54 pmol ml-1 h-1) on the 1st postnatal day when compared to the 7th day values (mean +/- SE: 27 +/- 5.7 pmol ml-1 h-1). Serial determinations showed a progressive decline from day 1 to day 7 after birth. We suggest the high serum DAO levels in neonates during the first days of life are due to leakage of placental enzyme into the circulation either at birth or during fetal life. Consequently, serum DAO cannot be used as a marker of small bowel functional integrity in the 1st postnatal week.