Evidence for a potential role of neuropeptide Y in ovine corpus luteum function

Keator, C.S.; Custer, E.E.; Hoagland, T.A.; Schreiber, D.T.; Mah, K.; Lawson, A.M.; Slayden, O.D.; McCracken, J.A.

doi:10.1016/j.domaniend.2009.08.003

« Previous Next »Domestic Animal Endocrinology
Volume 38, Issue 2 , Pages 103-114, February 2010

Evidence for a potential role of neuropeptide Y in ovine corpus luteum function

C.S. Keator
- Department of Animal Science, University of Connecticut, Storrs, CT 06269
- Corresponding author. Tel.: +1 503 614 3780; fax: +1 503 690 5563.
E.E. Custer
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655
T.A. Hoagland
- Department of Animal Science, University of Connecticut, Storrs, CT 06269
D.T. Schreiber
- Department of Animal Science, University of Connecticut, Storrs, CT 06269
K. Mah
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, USA
A.M. Lawson
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, USA
O.D. Slayden
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, USA
J.A. McCracken
- Department of Animal Science, University of Connecticut, Storrs, CT 06269

Received 8 January 2009; received in revised form 6 August 2009; accepted 7 August 2009. published online 27 September 2009.

Abstract

Neuropeptide Y (NPY) is a neurohormone that is typically associated with food intake, but it has also been reported to affect the production of progesterone from luteal tissue in vitro. However, NPY has not been previously immunolocalized in the ovine ovary or in the corpus luteum (CL) of any species, and the effects of this neurohormone on luteal function in vivo are not known. Thus, we performed fluorescent immunohistochemistry (IHC) to localize NPY in the ovine ovary and used avidin-biotin immunocytochemistry (ICC) to further define the intracellular localization within follicles and the CL. We then infused NPY directly into the arterial supply of the autotransplanted ovaries of sheep to determine the in vivo effect of exogenous NPY on ovarian blood flow and on the luteal secretion rate of progesterone and oxytocin. Immunohistochemistry revealed that the NPY antigen was localized to cells within the follicles and CL, in the nerve fibers of the ovarian stroma, and in the vessels of the ovarian hilus. In the follicle, the NPY antigen was localized to nerves and vessels within the theca interna layer, and strong staining was observed in the granulosal cells of antral follicles. In the CL, NPY was localized in large luteal cells and in the vascular pericytes and/or endothelial cells of blood vessels, found dispersed throughout the gland and within the luteal capsule. In vivo incremental infusions of NPY at 1, 10, 100, and 1,000 ng/min, each for a 30-min period, into the arterial supply of the transplanted ovary of sheep bearing a CL 11 d of age increased (P≤0.05) ovarian blood flow. The intra-arterial infusions of NPY also increased (P≤0.05) in a dose-dependent manner the secretion rate of oxytocin, which was positively correlated (P≤0.05) with the observed increase in ovarian blood flow. The infusions of NPY had a minimal effect on the secretion rate of progesterone, and similar intra-arterial infusions of NPY into sheep with ovarian transplants bearing a CL over 30 d of age had no significant effect on ovarian blood flow or on the secretion rate of progesterone. These results suggest that NPY acts on the luteal vascular system and the large luteal cells to rapidly stimulate blood flow and the secretion of oxytocin, respectively, which collectively implies a putative role for NPY during the process of luteolysis when increasing amounts of oxytocin are secreted from the ovine CL in response to uterine pulses of prostaglandin F2α.