The anterior pituitary (AP) gland functions as a storage and releasing unit for several hormones; growth hormone (GH), gonadotrophins (luteinizing hormone and follicle stimulating hormone), prolactin, adrenocorticotropin hormone, and tyroid stimulating hormone. Luteinizing hormone (LH) functions to increase ovarian follicular growth and maturation and responds to increasing concentrations of estradiol-17β (E2) that occur at estrus to cause ovulation. Production and secretion of the protein, insulin-like grwoth factor-I (IGF-I), occurs primarily in the liver, in response to GH release from the anterior pituitary gland. Insulin-like growth factor-I increases glucose uptake, amino acid transport, and glycogen synthesis resulting in increased protein accretion Mitogenic effects of IGF-I can be manifested by increases in DNA, RNA, and protein. Furthermore, IGF-I stimulates differentiation at low levels usually preceding a mitogenic response. The biological effects of IGF-I are mediated by its interaction with the IGF type 1 receptor and modulated by IGF binding proteins (IGFBPs). Insulin-like grwoth factor-I, IGFBPs, and IGF receptors have been detected in the AP gland of several species and may exert regulatory effects at the hypthalmaic-hypophyseal level affecting gonadotrophins, and in turn, reproductive performance.
Number of Pages
South Dakota State University
Copyright © 2001
Rempel, L.A. and Clapper, J.A., "Effects of Administration of Estradiol-17P on the
Serum and Anterior Pituitary IGF System in Pigs" (2002). South Dakota Swine Research Report, 2001. 18.