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Local IGF-I axis in peripubertal ruminant mammary development
R M Akers1, T B McFadden, S Purup
1Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, USA. rma@vt.edu
Journal of Mammary Gland Biology and Neoplasia
|May 3, 2000
Summary
Insulin-like growth factor-I (IGF-I) and IGF binding proteins are key local regulators of mammary development in peripubertal heifers. Their concentrations and interactions significantly influence udder growth, impacting overall development.
Area of Science:
- Reproductive biology
- Endocrinology
- Mammalian physiology
Background:
- Mammary gland growth and development involve complex hormonal and local factors.
- Estrogen and growth hormone are traditionally recognized for pubertal mammogenesis.
- Local growth factors within the mammary gland are influenced by nutritional and developmental status.
Purpose of the Study:
- To review the role of locally produced growth factors, specifically IGF-I and IGF-IBPs, in regulating mammary development in peripubertal ruminants.
- To investigate the impact of nutritional status on mammary growth and associated growth factor concentrations.
Main Methods:
- Review of existing studies on heifer mammary development.
- Analysis of data from ovariectomized heifers to assess the role of IGF-I and IGFBP-3.
- Examination of in vitro studies demonstrating the mitogenic activity of IGF-I and IGFBP-3.
Main Results:
- IGF-I and IGF binding proteins (IGFBPs) are crucial local regulators of mammary growth in peripubertal ruminants.
- Reduced mammary development in ovariectomized heifers correlated with altered IGF-I and IGFBP-3 levels.
- Overfeeding in heifers led to reduced mammary development, decreased tissue mitogenic activity, and altered IGF-I/IGFBP concentrations.
Conclusions:
- Local mammary-derived growth factors, particularly IGF-I and its binding proteins, play a significant role in mammogenesis.
- These local factors likely mediate many effects previously attributed to systemic mammogenic hormones.
- IGFBP-3 concentration modulates the effectiveness of IGF-I in mammary tissue growth.