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Tissue-specific effects of castration and ovariectomy on murine epidermal growth factor and its mRNA
J C Pascall1, J Saunders, D M Blakeley
1Department of Biochemistry, AFRC Institute of Animal Physiology and Genetics Research, Cambridge Research Station.
Abstract:
The polypeptide mitogen, epidermal growth factor (EGF), was originally isolated from mouse submaxillary gland (SMG). In mice, these glands are sexually dimorphic; the SMG of male animals typically contains up to 400 pmol EGF/mg protein whereas EGF concentrations in the SMG of female mice are only 5-20 pmol/mg protein. When mice were castrated at 8 weeks of age, EGF mRNA levels in the SMG fell rapidly to the low levels observed in control female animals. Although the concentration of EGF in the SMG, measured by radioimmunoassay, also fell to very low levels (13.8 +/- 0.7 (S.E.M.) pmol/mg protein) in the castrated mice, the rate of decrease was considerably slower than that of the mRNA. In contrast to the loss of EGF and EGF mRNA from mice following castration, ovariectomy led to a rise in EGF mRNA levels in SMG, with a maximal increase (approximately 100-fold) 4-6 weeks after ovariectomy. Concentrations of EGF in the SMG also rose markedly in the ovariectomized animals, from a control value of 5.4 +/- 0.8 to 34.7 +/- 7.9 pmol/mg protein at 6 weeks. In mice, the kidney displays the second highest level of EGF gene expression. However, in contrast to the effects on SMG, kidney EGF mRNA was not affected by either castration or ovariectomy. These results provide further evidence for the tissue-specific control of EGF gene expression in response to steroid hormones.
Insights
Steroid hormones significantly impact epidermal growth factor (EGF) levels in mouse submaxillary glands (SMG). Castration reduces EGF and its mRNA, while ovariectomy increases them, demonstrating tissue-specific hormonal control.
Area of Science:
- Endocrinology
- Molecular Biology
- Developmental Biology
Background:
- Epidermal growth factor (EGF) is a polypeptide mitogen originally isolated from the mouse submaxillary gland (SMG).
- Mouse SMG exhibits sexual dimorphism in EGF concentration, with males having significantly higher levels than females.
Purpose of the Study:
- To investigate the influence of sex steroid hormones on epidermal growth factor (EGF) gene expression and protein levels in the mouse submaxillary gland (SMG) and kidney.
Main Methods:
- Surgical castration and ovariectomy were performed on mice at 8 weeks of age.
- Epidermal growth factor (EGF) mRNA levels were measured using quantitative assays.
- EGF protein concentrations in the SMG were determined by radioimmunoassay.
Main Results:
- Castration in male mice led to a rapid decrease in SMG EGF mRNA and a slower decline in EGF protein levels.
- Ovariectomy in female mice resulted in a substantial increase in SMG EGF mRNA (up to 100-fold) and EGF protein concentration.
- Kidney EGF mRNA levels remained unaffected by either castration or ovariectomy, indicating tissue-specific responses.
Conclusions:
- Sex steroid hormones play a critical role in regulating epidermal growth factor (EGF) gene expression in a tissue-specific manner within the mouse submaxillary gland.
- These findings highlight the differential control of EGF production by hormonal signals in distinct organs.