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Hormonal and Spatial Regulation of Nitric Oxide Synthases (NOS) (Neuronal NOS, Inducible NOS, and Endothelial NOS) in the Oviducts

Unité de Recherche en Ontogénie et Reproduction (J.L., M.R., I.S.-P., D.G., J.-F.B.), Centre de Recherche du Centre Hospitalier de l’Université Laval, and Centre de Recherche en Biologie de la Reproduction (J.L., M.R., I.S.-P., D.G., J.-F.B.), Université Laval, Québec, Canada G1V 4G2; Department of Plant and Animal Sciences (S.K., L.A.M.), Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3; and Département d’Obstétrique et Gynécologie (J.-F.B.), Faculté de Médecine, Université Laval, Québec, Canada G1K 7P4

Address all correspondence and requests for reprints to: Jean-François Bilodeau, Unité d’Ontogénie et Reproduction, Local T-1-49, 2705 Boulevard Laurier, Ste-Foy, Québec, Canada G1V 4G2. E-mail: jean-francois.bilodeau{at}crchul.ulaval.ca.

Nitric oxide (NO) is a free radical produced by the action of NO synthases (NOS) and is known to be involved in the regulation of many reproductive events that occur in the oviducts. The oviducts are highly specialized organs that play crucial roles in reproduction by providing an optimal environment for the final maturation of gametes, fertilization, and early embryo development. In this study, we analyzed the expression, hormonal regulation, and cellular distribution of neuronal, inducible, and endothelial NOS in different bovine oviduct segments to better understand the roles played by these enzymes in oviductal functions in vivo. Quantitative RT-PCR analysis revealed that NOS isoforms are hormonally regulated and differentially expressed along the oviduct throughout the estrous cycle. All NOS were highly expressed around the time of estrus, and immunohistochemistry studies determined that neuronal NOS, inducible NOS (iNOS), and endothelial NOS are differentially distributed in cells along the oviduct. Interestingly, our results showed that estradiol selectively up-regulates iNOS expression in the oviduct during the periovulatory period corresponding to the window of ovulation, oocyte transport, and fertilization. The resulting NO production by this high-output NOS may be of crucial importance for reproductive events that occur in the oviduct. This study provided the first demonstration that NO production is hormonally regulated in the mammalian oviducts in vivo. Our results suggest that neuronal NOS, iNOS, and endothelial NOS contribute to oviductal functions in a timely and site-specific manner.