The Insulin-like Growth Factor System: a Key Determinant Role in the Growth and Selection of Ovarian Follicles? A Comparative Species Study

• Published in: Reproduction in domestic animals 2003-08, Vol.38 (4), p.247-258
• Main Authors: Mazerbourg, S, Bondy, CA, Zhou, J, Monget, P
• Format: Article
• Language: English
• Subjects: Animals; Animals, Domestic - metabolism; Biological and medical sciences; Computer Science; Female; Fundamental and applied biological sciences. Psychology; Gene Expression; Hormone metabolism and regulation; Insulin-Like Growth Factor Binding Protein 2 - metabolism; Insulin-Like Growth Factor Binding Protein 4 - metabolism; Insulin-Like Growth Factor Binding Proteins - metabolism; Life Sciences; Mammalian female genital system; Ovarian Follicle - physiology; Receptor, IGF Type 1 - metabolism; RNA, Messenger - metabolism; Somatomedins - metabolism; Species Specificity; Vertebrates: reproduction
• ISSN: 0936-6768; 1439-0531
• DOI: 10.1046/j.1439-0531.2003.00440.x

Contents The aim of the present paper is to make a comparative study of the expression of the elements of the insulin‐like growth factor (IGF) system in different mammalian species and thus illuminate their potential role in the process of ovarian folliculogenesis in mammals. In most mammalian species, IGFs and IGFBPs (in particular IGFBP‐2 and IGFBP‐4) are considered, respectively, as stimulators and inhibitors of follicular growth and maturation. In mammalian species, IGFs might play a key role in sensitizing ovarian granulosa cells to FSH action during terminal follicular growth. Concentrations of IGFBP‐2 and IGFBP‐4 in follicular fluid strongly decrease and increase during follicular growth and atresia, respectively, leading to an increase and a decrease in IGF bioavailability, respectively. The decrease in these IGFBPs is because of a decrease in mRNA expression (IGFBP‐2) and an increase in proteolytic degradation by PAPP‐A in follicular fluid (IGFBP‐2, IGFBP‐4 and IGFBP‐5), and likely participates in the selection of dominant follicles. In contrast, levels and/or sites of expression of IGF‐I, IGF‐II, IGFBP‐4, IGFBP‐5 and type II receptor in follicular cells strongly differ between mammalian species, suggesting that these phenomena might play species‐specific or secondary roles in ovarian folliculogenesis.