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Perinatal evolution and hormonal control of adrenal tyrosine hydroxylase activity in the rat

A Aminot, J Roffi

    Enzyme
    |January 1, 1979
    PubMed

    Insights

    Adrenal tyrosine hydroxylase activity in fetal rats increases gradually, with a sharp rise after birth, likely due to birth stress. Adrenocorticotropic hormone (ACTH) directly influences this activity in fetal adrenal glands.

    Area of Science:

    • Developmental biology
    • Neuroendocrinology
    • Biochemistry

    Background:

    • Adrenal tyrosine hydroxylase (TH) is a key enzyme in catecholamine synthesis.
    • Its developmental regulation in the perinatal period is not fully understood.
    • Previous studies suggest hormonal and neural influences on TH activity.

    Purpose of the Study:

    • To investigate the developmental pattern of adrenal tyrosine hydroxylase activity in fetal and neonatal rats.
    • To explore the roles of nervous mechanisms and hormones (ACTH, cortisol) in regulating this activity during the perinatal period.

    Main Methods:

    • Measurement of adrenal tyrosine hydroxylase activity in rat fetuses from 18.5 days of gestation to 24 hours postpartum.
    • Surgical decapitation of fetuses to assess the role of the central nervous system.
    • Administration of adrenocorticotropic hormone (ACTH) and cortisol to decapitated fetuses.

    Main Results:

    • Adrenal TH activity showed a gradual increase during fetal development, followed by a rapid, transient surge between 0-6 hours postpartum.
    • Fetal decapitation significantly reduced term adrenal TH activity.
    • Administration of ACTH partially restored TH activity in decapitated fetuses, while cortisol had no significant effect.

    Conclusions:

    • A nervous mechanism, possibly related to birth stress, contributes to the postpartum surge in adrenal TH activity.
    • Adrenocorticotropic hormone (ACTH) exerts a direct regulatory effect on adrenal tyrosine hydroxylase activity in the fetal rat, similar to its action in adults.

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