Catabolic regulation of blood cortisol in premature and term baboon neonates

Abstract

The metabolism of I.V. administered 4-[14C]-cortisol (F) was examined in 3 premature (cesarean section at 160, 167, and 174 days gestation, term = 184 days) and 8 spontaneously delivered term (184 ± 2 days) baboon neonates (Papio papio). Three premature (Group 1) and 4 spontaneously delivered animals (Group 2) were studied 2–18 h after delivery and, the remainder on the 5th (N = 2) or 12th (N = 2) day of life (Group 3). [14C]-Metabolites were isolated by ehromatography and crystallization. More than 10% of 14C was in liver, 3–9% in intestine and brain, ≤ 2% in lung, kidney, heart, spleen, and urine, and < 0.2%/g in blood and muscle 30 min. after injection. Most 14C (77.5 ± 1.6%) in all tissues was unconjugated. Extrahepatic tissues were primarily responsible for oxidation of F to cortisone. Formation of tetrahydrocortisol (THF), tetrahydrocortisone (THE), two hydroxylated metabolites and glucuronoside conjugates was restricted to liver. Alterations in F metabolism (decreased hydroxylated metabolites, increased THF and THE glucuronides) were not evident until 5–12 days after delivery. It is concluded that extrahepatic 11β-hydroxysteroid dehydrogenase is important in achieving a low F:E ratio in fetal blood. The similarity in F catabolic patterns of premature and day 1 term newborns makes it unlikely that changes in metabolism can account for the increased fetal blood F concentrations prior to parturition.