[Significance of the adrenal medulla and brain catecholamine in perinatal period: their developmental changes and responses to hypoxia in fetal rats].

To elucidate the significance of adrenal medulla and brain catecholamines (CA) in perinatal adaptation, their developmental changes, responses to hypoxia and the relation between brain energy metabolism and secreted CA were investigated using fetal rats. The following results were obtained. Adrenal norepinephrine (NE) showed a gradual linear increase during the last week of gestation. Epinephrine (E) increased rapidly during the last 3 days to become predominant over NE. A gradual increase in brain NE was observed with advancing gestational age. In the term fetal rats, adrenal NE and E decreased significantly by 18.7% and 17.0% respectively after 30 minutes of hypoxia in utero. Brain NE decreased significantly during both hypoxia and recovery up to 60 minutes. The blood glucose levels were elevated markedly, reaching a peak at 30 minutes of recovery which corresponded to the peak of diminution of adrenal CA. The brain energy charge potential [(ATP) + 0.5(ADP)]/[(ATP) + (ADP) + (AMP)] fell significantly during hypoxia, followed by rapid recovery after hypoxia. It is concluded that matured fetal adrenal medulla responds to acute hypoxia, discharging both NE and E with sufficient reserve, and secreted CA plays an important role in maintaining the brain energy level during recovery after hypoxia. And the changes in brain NE content caused by hypoxia may be a causative factor in the neurological sequela of hypoxia.