title: Formation of the early canine CL and the role of prostaglandin E2 (PGE2) in regulation of its function: an in vivo approach.
abstract: The mechanisms governing corpus luteum (CL) function in domestic dogs remain not fully elucidated. The upregulated expression of cyclooxygenase 2 and prostaglandin (PG) E2 synthase (PGES) at the beginning of the canine luteal phase indicated their luteotrophic roles, and the steroidogenic activity of PGE2 in the early canine CL has been confirmed in vitro. Recently, by applying a cyclooxygenase 2 (COX2)-specific inhibitor (firocoxib [Previcox]; Merial) from the day of ovulation until the midluteal phase, the luteotrophic effects of PGs have been shown in vivo. This is a follow-up study investigating the underlying endocrine mechanisms associated with the firocoxib-mediated effects on the canine CL. Experimental groups were formed with ovariohysterectomies performed on Days 5, 10, 20, or 30 of firocoxib treatments (10 mg/kg bw/24h; TGs = treated groups). Untreated dogs served as controls. A decrease of steroidogenic acute regulatory (STAR) protein expression was observed in TGs. The expression of PGE2 synthase was significantly suppressed in TGs 5 and 10, and both PGE2 and PGF2α levels were decreased in luteal homogenates, particularly from CL in TG 5. Similarly, expression of the prolactin receptor (PRLR) was diminished in TGs 5 and 20. The expression of PGE2 receptors PTGER2 (EP2) and PTGER4 (EP4), the PG- transporter (PGT), and 15-hydroxy PG dehydrogenase (HPGD) was not affected in TGs. Our results substantiate a direct luteotrophic role of PGs in the early canine CL, i.e., by upregulating the steroidogenic machinery. Additionally, the possibility of an indirect effect on PRL function arises from the increased prolactin receptor expression in response to PGE2 treatment in canine lutein cells observed in vitro.
authors.affiliation: Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: kowalewskipl@yahoo.de.
authors.forename: M P
authors.initials: MP
authors.lastname: Kowalewski
authors.affiliation: Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Ihle
authors.affiliation: Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Siemieniuch
authors.affiliation: Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Gram
authors.affiliation: Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Boos
authors.affiliation: Department of Animal Reproduction, University of Warmia and Mazury, Olsztyn, Poland.
authors.forename: S
authors.initials: S
authors.lastname: Zduńczyk
authors.affiliation: Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Fingerhut
authors.affiliation: Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Hoffmann
authors.affiliation: Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schuler
authors.affiliation: Department of Animal Reproduction, University of Warmia and Mazury, Olsztyn, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Jurczak
authors.affiliation: Department of Animal Reproduction, University of Warmia and Mazury, Olsztyn, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Domosławska
authors.affiliation: Department of Animal Reproduction, University of Warmia and Mazury, Olsztyn, Poland.
authors.forename: T
authors.initials: T
authors.lastname: Janowski
mesh_terms: D015107:4-Butyrolactone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D003338:Corpus Luteum / Q000254:growth & development*; D015237:Dinoprost / Q000235:genetics / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D004285:Dogs / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D019746:Intramolecular Oxidoreductases / Q000235:genetics / Q000378:metabolism; D008297:Male; D000071876:Prostaglandin-E Synthases; D011982:Receptors, Prostaglandin / Q000235:genetics / Q000378:metabolism; D013450:Sulfones / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D011982:Receptors, Prostaglandin; D013450:Sulfones; D015237:Dinoprost; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone; D015107:4-Butyrolactone; C487384:firocoxib
keywords: CL; Dog (Canis familiaris); Prostaglandin