Postnatal changes in urinary prostaglandin E excretion in premature infants.

Urinary PGE excretion was measured by radioimmunoassay in a group of 11 healthy premature infants with a mean birth weight of 1,502 g (range 1,050--1,950 g) and a mean gestational age of 31.6 weeks (range 29--33 weeks), respectively. Measurements were made on the 7th day of life and at weekly intervals thereafter until the 5th week of life. It was demonstrated that urinary PGE excretion significantly increased from the very low level of 6.23 +/- 0.70 ng/24 h (mean +/- SE) on the 7th day to a value of 17.99 +/- 3.53 ng/24 h by the end of the 3rd week (p less than 0.005). Later on it remained practically unchanged. It is suggested that its rapid increase during the first 3 weeks of life may be the result of the highly elevated activity of the renin-angiotensin-aldosterone system and it may play a role in controlling renal blood flow.