Studies on shrew (Suncus murinus) epidermal growth factor

Area of Science:

• Endocrinology
• Developmental Biology
• Comparative Physiology

Background:

• Epidermal Growth Factor (EGF) is a potent mitogen crucial for cell growth and differentiation.
• The shrew submandibular gland (SMG) is known for high EGF content, but its characteristics and physiological roles require further investigation.

Purpose of the Study:

• To quantify EGF levels in shrew SMG and other tissues.
• To investigate the sex dependency of EGF levels.
• To explore the biological activity and molecular forms of shrew EGF.

Main Methods:

• Heterologous radioreceptor assay for EGF quantification.
• Tissue analysis across various shrew organs.
• Gel chromatography for molecular form identification.
• Bioassays using neonatal rat pups to assess EGF activity.

Main Results:

• Male shrew SMG exhibits very high EGF levels (~300 pmol/mg), significantly exceeding female levels (4%).
• A reciprocal distribution of EGF and EGF receptor was observed between the SMG, parotid gland, and liver.
• Shrew EGF demonstrated heat stability and induced precocious eyelid opening and incisor eruption in rat pups at low doses.
• No high molecular weight EGF forms were detected in adult tissues, but fetal samples revealed multiple forms.

Conclusions:

• The exceptionally high, sex-dependent EGF levels in shrew SMG likely contribute to the species' active lifestyle and rapid pup growth.
• Shrew EGF exhibits potent biological activity, comparable to mammalian EGF, suggesting conserved physiological functions.
• The presence of multiple EGF forms in fetuses indicates complex developmental regulation of EGF expression.