Endocrinology, Vol 136, 62-68, Copyright © 1995 by Endocrine Society

ARTICLES

Insulin-like growth factor-I (IGF-I) and IGF-binding proteins in bovine sera and pituitaries at different stages of the estrous cycle

RN Funston, GE Moss and AJ Roberts
University of Wyoming, Laramie 82071.

The objective of this study was to determine whether concentrations of hypophyseal and serum insulin-like growth factor-I (IGF-I) and binding activities of serum and hypophyseal IGF-binding proteins (IGFBPs) differ with stage of the estrous cycle in mature beef cows. Cows were assigned to the following stages of the estrous cycle based on serum concentrations of progesterone (P4) and ovarian structures at death: days 1-5 (day 0 = estrus; n = 18), days 6-10 (n = 24), days 11-16 (n = 39), and days 17-21 (n = 7). Serum samples collected at death and anterior pituitary homogenates were analyzed for IGF-I, LH, and FSH by RIA. Serum and pituitary IGFBPs were evaluated by ligand and immunoblot analyses. Serum samples contained IGFBP activity at 44 and 40 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 30 kDa (IGFBP-5), 28 kDa, and 24 kDa. The intensity of binding by the different sized proteins in serum remained constant throughout the estrous cycle. IGFBPs detected in anterior pituitaries included a 36-/40-kDa doublet (IGFBP-3), a 32- kDa protein (IGFBP-2), and a 29-kDa IGFBP (IGFBP-5). The intensity of [125I]IGF-I binding to IGFBPs was greater (P < 0.05) during days 11-16 than days 1-5 or days 6-10 of the estrous cycle and was intermediate (P > 0.05) during days 17-21. Serum concentrations of LH were low (< 0.4 ng/ml) during days 1-16 of the estrous cycle, but increased (P < 0.05) approximately 3- to 4-fold during days 17-21. LH concentrations in the anterior pituitary increased (P < 0.05) from the postovulatory period (548 +/- 52 micrograms/g; days 1-5) to the late luteal phase (791 +/- 39 micrograms/g; days 11-16) and were intermediate (P > 0.05) during the preovulatory phase (707 +/- 85 micrograms/g; days 17-21). Concentrations of IGF-I and FSH in the anterior pituitary and serum did not differ (P > 0.05) by stage of the estrous cycle. A positive correlation among the different IGFBPs in the pituitary (P < 0.01) and between each pituitary IGFBP and serum P4 (P < 0.05) existed. The significance (P < 0.0002) of the correlation between pituitary IGFBP-3 and P4 was greater (P < 0.02) than that between the other pituitary IGFBPs and P4. In summary, IGFBP activity in the anterior pituitary, but not that in serum, changed with stage of the estrous cycle in association with serum concentrations of P4. The absence of similar changes in serum or anterior pituitary concentrations of IGF-I supports the hypothesis that IGFBPs may regulate the actions of IGF-I on gonadotropin release from the anterior pituitary gland during the estrous cycle of beef cattle.

This article has been cited by other articles:

				E. J. Scholljegerdes, B. W. Hess, M. H. J. Grant, S. L. Lake, B. M. Alexander, T. R. Weston, D. L. Hixon, E. A. Van Kirk, and G. E. Moss Effects of feeding high-linoleate safflower seeds on postpartum reproduction in beef cows J Anim Sci, September 1, 2009; 87(9): 2985 - 2995. [Abstract] [Full Text] [PDF]

				C. L. Engel, H. H. Patterson, and G. A. Perry Effect of dried corn distillers grains plus solubles compared with soybean hulls, in late gestation heifer diets, on animal and reproductive performance J Anim Sci, July 1, 2008; 86(7): 1697 - 1708. [Abstract] [Full Text] [PDF]

				X. Qin, J. E. Wergedal, M. Rehage, K. Tran, J. Newton, P. Lam, D. J. Baylink, and S. Mohan Pregnancy-Associated Plasma Protein-A Increases Osteoblast Proliferation in Vitro and Bone Formation in Vivo Endocrinology, December 1, 2006; 147(12): 5653 - 5661. [Abstract] [Full Text] [PDF]

				C K Hilleson-Gayne and J A Clapper Effects of decreased estradiol-17{beta} on the serum and anterior pituitary IGF-I system in pigs J. Endocrinol., December 1, 2005; 187(3): 369 - 378. [Abstract] [Full Text] [PDF]

				A. Kumar, S. Mohan, J. Newton, M. Rehage, K. Tran, D. J. Baylink, and X. Qin Pregnancy-associated Plasma Protein-A Regulates Myoblast Proliferation and Differentiation through an Insulin-like Growth Factor-dependent Mechanism J. Biol. Chem., November 11, 2005; 280(45): 37782 - 37789. [Abstract] [Full Text] [PDF]

				B. W. Hess, S. L. Lake, E. J. Scholljegerdes, T. R. Weston, V. Nayigihugu, J. D. C. Molle, and G. E. Moss Nutritional controls of beef cow reproduction J Anim Sci, June 1, 2005; 83(13_suppl): E90 - 106. [Abstract] [Full Text] [PDF]

				J. D. Veldhuis, S. M. Anderson, A. Iranmanesh, and C. Y. Bowers Testosterone Blunts Feedback Inhibition of Growth Hormone Secretion by Experimentally Elevated Insulin-Like Growth Factor-I Concentrations J. Clin. Endocrinol. Metab., March 1, 2005; 90(3): 1613 - 1617. [Abstract] [Full Text] [PDF]

				Z. Kiyma, B. M. Alexander, E. A. Van Kirk, W. J. Murdoch, D. M. Hallford, and G. E. Moss Effects of feed restriction on reproductive and metabolic hormones in ewes J Anim Sci, September 1, 2004; 82(9): 2548 - 2557. [Abstract] [Full Text] [PDF]

				R. P. Wettemann, C. A. Lents, N. H. Ciccioli, F. J. White, and I. Rubio Nutritional- and suckling-mediated anovulation in beef cows J Anim Sci, February 1, 2003; 81(14_suppl_2): E48 - 59. [Abstract] [Full Text] [PDF]

				M. L. Looper, J. A. Vizcarra, R. P. Wettemann, J. R. Malayer, T. D. Braden, R. D. Geisert, and G. L. Morgan Influence of estradiol, progesterone, and nutrition on concentrations of gonadotropins and GnRH receptors, and abundance of mRNA for GnRH receptors and gonadotropin subunits in pituitary glands of beef cows J Anim Sci, January 1, 2003; 81(1): 269 - 278. [Abstract] [Full Text] [PDF]

				J. D. Bottger, B. W. Hess, B. M. Alexander, D. L. Hixon, L. F. Woodard, R. N. Funston, D. M. Hallford, and G. E. Moss Effects of supplementation with high linoleic or oleic cracked safflower seeds on postpartum reproduction and calf performance of primiparous beef heifers J Anim Sci, August 1, 2002; 80(8): 2023 - 2030. [Abstract] [Full Text] [PDF]

				Y. Wu, S. Yakar, L. Zhao, L. Hennighausen, and D. LeRoith Circulating Insulin-like Growth Factor-I Levels Regulate Colon Cancer Growth and Metastasis Cancer Res., February 1, 2002; 62(4): 1030 - 1035. [Abstract] [Full Text] [PDF]

				A. Quesada and A. M. Etgen Insulin-Like Growth Factor-1 Regulation of {{alpha}}1-Adrenergic Receptor Signaling Is Estradiol Dependent in the Preoptic Area and Hypothalamus of Female Rats Endocrinology, February 1, 2001; 142(2): 599 - 607. [Abstract] [Full Text] [PDF]

				J.L. Snyder, J.A. Clapper, A.J. Roberts, D.W. Sanson, D.L. Hamernik, and G.E. Moss Insulin-Like Growth Factor-I, Insulin-Like Growth Factor-Binding Proteins, and Gonadotropins in the Hypothalamic-Pituitary Axis and Serum of Nutrient-Restricted Ewes Biol Reprod, July 1, 1999; 61(1): 219 - 224. [Abstract] [Full Text]

				J.A. Clapper, J.L. Snyder, A.J. Roberts, D.L. Hamernik, and G.E. Moss Estradiol Increases Relative Amounts of Insulin-Like Growth Factor Binding Protein (IGFBP)-3 in Serum and Expression of IGFBP-2 in Anterior Pituitaries of Ewes Biol Reprod, July 1, 1998; 59(1): 124 - 130. [Abstract] [Full Text]

				M.L. Keller, A.J. Roberts, and G.E. Seidel Jr. Characterization of Insulin-Like Growth Factor-Binding Proteins in the Uterus and Conceptus during Early Conceptus Elongation in Cattle Biol Reprod, July 1, 1998; 59(3): 632 - 642. [Abstract] [Full Text]

				J. A. Vizcarra, R. P. Wettemann, T. D. Braden, A. M. Turzillo, and T. M. Nett Effect of Gonadotropin-Releasing Hormone (GnRH) Pulse Frequency on Serum and Pituitary Concentrations of Luteinizing Hormone and Follicle-Stimulating Hormone, GnRH Receptors, and Messenger Ribonucleic Acid for Gonadotropin Subunits in Cows Endocrinology, February 1, 1997; 138(2): 594 - 601. [Abstract] [Full Text] [PDF]