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Expression of LGR7 and LGR8 by Neonatal Porcine Uterine Tissues and Transmission of Milk-Borne Relaxin into the Neonatal Circulation by Suckling

Department of Animal Sciences (W.Y., A.-L.F., C.A.B.), Rutgers University, New Brunswick, New Jersey 08901; Department of Animal Sciences, Cellular and Molecular Biosciences Program (A.A.W., B.D.C., F.F.B.), Auburn University, Auburn, Alabama 26849; Howard Florey Institute (R.A.D.B.), University of Melbourne, Victoria 3010, Australia; and Department of Environmental Medicine (S.L., B.G.S.), Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987

Address all correspondence and requests for reprints to: Dr. Frank F. Bartol, Department of Animal Sciences, Upchurch Hall, Auburn University, Auburn, Alabama 36849-5415. E-mail: bartoff{at}auburn.edu.

Estrogen receptor-dependent organizational events between birth [postnatal day (PND) 0] and PND 14 affect development and function of porcine uterine tissues. Observations that uterotrophic effects of relaxin (RLX) in neonatal gilts were inhibited by the antiestrogen ICI 182,780 suggested that a RLX signaling system, capable of cross-talk with the estrogen receptor, evolves during a critical period for uterine programming (PND 0–14). Objectives were to determine 1) effects of age and estrogen exposure from birth on porcine uterine RLX/insulin-like 3 receptor (LGR7/LGR8) expression and 2) whether milk serves as a natural source of RLX in neonatal pigs. Uterine LGR7/LGR8 expression, detected by RT-PCR and in situ hybridization on PND 0, 7, and 14, was predominantly stromal for LGR7, myometrial for LGR8, and increased with age and after treatment with estradiol valerate (50 µg/kg body weight·d) from birth. Stromal expression of LGR7 was also detected immunohistochemically. Milk RLX concentrations declined (P < 0.001) from 17.3 ± 1.4 ng/ml (lactation d 0) to 1.7 ± 0.3 ng/ml (lactation d 14). RLX, present in the serum of nursing pigs on PND 0 and 1, was undetectable before nursing and in neonates fed RLX-free milk replacer for 12 h. Thus, a developmentally regulated, estrogen-sensitive LGR7 and LGR8 receptor system is present in the porcine uterus at birth and may be activated by milk-borne RLX delivered into the circulation during the first 48 h of postnatal life. Maternal lactocrine contributions to the neonatal hormonal milieu could affect the developmental programming of uterine and other somatic tissues.

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				W. Yan, J. Chen, A. A Wiley, B. D Crean-Harris, F. F Bartol, and C. A Bagnell Relaxin (RLX) and estrogen affect estrogen receptor {alpha}, vascular endothelial growth factor, and RLX receptor expression in the neonatal porcine uterus and cervix Reproduction, May 1, 2008; 135(5): 705 - 712. [Abstract] [Full Text] [PDF]