Journal of Animal Science, Vol 70, Issue 9 2911-2923, Copyright © 1992 by American Society of Animal Science

JOURNAL ARTICLE

Ruminant placental lactogens: structure and biology

J. C. Byatt, W. C. Warren, P. J. Eppard, N. R. Staten, G. G. Krivi and R. J. Collier
Animal Sciences Division, Monsanto Company, St. Louis, MO 63198.

Ruminant placental lactogens (PL) are members of the somatotropin, prolactin gene family that are synthesized by trophectodermal binucleate cells. The structure and biology of PL has been studied in the cow, sheep, and goat. Ruminant PL have greater structural identity to prolactin than somatotropin, although they bind to both lactogenic and somatogenic receptors. The molecular weights of ovine and caprine PL are approximately 23,000, whereas bovine PL is larger (31,000 to 34,000) due to glycosylation. Placental lactogen is secreted into both the fetal and maternal circulations. The concentration of PL in the fetus decreases with advancing gestation, whereas PL concentration peaks in the maternal circulation during the last third of pregnancy then reaches a plateau. Furthermore, the maternal concentration of PL is 100- to 1,000-fold higher in sheep and goats than in cows. The precise factors that modulate secretion of PL are unknown, although placental mass and nutrition seem to play a role. Ruminant PL have both lactogenic and somatogenic biological activities and may also have unique activities mediated through a specific receptor. There is circumstantial evidence to suggest that PL plays a role in stimulating mammogenesis. Placental lactogen secreted into the fetal compartment may also help regulate fetal growth. Direct experimental data indicate that PL can regulate maternal intermediary metabolism. Thus, it may act as a partitioning agent to regulate nutrient supply for fetal growth. The precise biological function of PL in ruminants, therefore, still needs to be defined.

This article has been cited by other articles:

				T. M. Sullivan, G. C. Micke, N. Perkins, G. B. Martin, C. R. Wallace, K. L. Gatford, J. A. Owens, and V. E. A. Perry Dietary protein during gestation affects maternal insulin-like growth factor, insulin-like growth factor binding protein, leptin concentrations, and fetal growth in heifers J Anim Sci, October 1, 2009; 87(10): 3304 - 3316. [Abstract] [Full Text] [PDF]

				M. Bertolini, C. R Wallace, and G. B Anderson Expression profile and protein levels of placental products as indirect measures of placental function in in vitro-derived bovine pregnancies Reproduction, January 1, 2006; 131(1): 163 - 173. [Abstract] [Full Text] [PDF]

				S. R. Ravelich, A. N. Shelling, A. Ramachandran, S. Reddy, J. A. Keelan, D. N. Wells, A. J. Peterson, R. S.F. Lee, and B. H. Breier Altered Placental Lactogen and Leptin Expression in Placentomes from Bovine Nuclear Transfer Pregnancies Biol Reprod, December 1, 2004; 71(6): 1862 - 1869. [Abstract] [Full Text] [PDF]

				M.-C. Lacroix, E. Devinoy, S. Cassy, J.-L. Servely, M. Vidaud, and G. Kann Expression of Growth Hormone and Its Receptor in the Placental and Feto-Maternal Environment during Early Pregnancy in Sheep Endocrinology, December 1, 1999; 140(12): 5587 - 5597. [Abstract] [Full Text]

				A. Herman, D. Helman, O. Livnah, and A. Gertler Ruminant Placental Lactogens Act as Antagonists to Homologous Growth Hormone Receptors and as Agonists to Human or Rabbit Growth Hormone Receptors J. Biol. Chem., March 19, 1999; 274(12): 7631 - 7639. [Abstract] [Full Text] [PDF]