Epidermal growth factor in the developing mammal.

Area of Science:

• Cell Biology
• Developmental Biology
• Endocrinology

Background:

• Epidermal growth factor (EGF) is a key mammalian growth factor with incompletely understood roles.
• EGF receptors are present in fetal tissues, suggesting a potential role in embryogenesis and fetal growth.
• Alpha transforming growth factor (alpha TGF) may subserve a developmental role in the fetus, acting via EGF receptors.

Purpose of the Study:

• To elucidate the precise roles and significance of EGF in mammalian development and function.
• To investigate the presence and localization of EGF and its mRNA in fetal and postnatal animals.
• To explore the influence of hormonal signals on EGF production and action.

Main Methods:

• Detection of EGF mRNA in fetal and postnatal tissues.
• Immunohistochemical analysis of EGF and EGF receptors.
• Hormonal manipulation studies to assess EGF responsiveness.

Main Results:

• EGF mRNA is not detected in the fetus, but alpha TGF mRNA is present.
• Postnatal animals exhibit EGF mRNA, immunoreactive EGF, and EGF receptors in various tissues, notably salivary glands and kidneys.
• Tissue EGF concentrations and synthesis are hormone-responsive, influenced by thyroid and gonadal steroids.

Conclusions:

• Alpha TGF, not EGF, appears to be the primary developmental factor in the fetus.
• Postnatal EGF likely contributes to the maintenance of epithelial surface integrity in the gut and urinary tract.
• EGF exerts mitogenic and developmental effects through autocrine, paracrine, and potentially endocrine routes, modulated by hormonal signals.