Apelin system detection in the reproductive apparatus of ewes grazing on semi-natural pasture

• Published in: Theriogenology 2019-11, Vol.139, p.156-166
• Main Authors: Mercati, Francesca, Scocco, Paola, Maranesi, Margherita, Acuti, Gabriele, Petrucci, Linda, Cocci, Paolo, Renzi, Asia, De Felice, Elena, Dall’Aglio, Cecilia
• Format: Article
• Language: English
• Subjects: Animals; Apelin - genetics; Apelin - metabolism; Apelin - physiology; Apelin Receptors - genetics; Apelin Receptors - metabolism; Apelin Receptors - physiology; APLN; APLNR; Female; Genitalia - metabolism; Immunohistochemistry; Ovary; Ovary - metabolism; Ovary - pathology; Oviduct; Oviducts - metabolism; Oviducts - pathology; Sheep; Uterus; Uterus - metabolism; Uterus - pathology
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2019.08.012

Apelin (APLN) is an adipokine with pleiotropic effects involved in the regulation of metabolic, cardiovascular, immune, and electrolyte balance function. Recent studies demonstrated a pivotal role in the regulation of male and female reproduction. APLN and its receptor (APLNR) were found in the hypothalamic-pituitary-gonad axis tissues, regulating gonadotropin release and steroidogenesis. However, to date, there are no studies that describe APLN system in the reproductive apparatus of the sheep. The study was performed on 10 Comisana x Appenninica adult dry ewes reared in a semi-natural pasture. Organ samples were collected from five animals in the two pasture functional phases: after maximum pasture flowering (Group 1) and after maximum pasture dryness (Group 2). Experiments were devised to characterize the gene expression and protein localization of the APLN/APLNR system in ewe reproductive apparatus; in addition, the concentration of plasma APLN was evaluated during the trial. Through immunohistochemical analysis, a positive staining for APLN was observed in the large luteal cells, in the epithelial cell coat of the ampulla, in the uterus epithelial lining and in the uterine glands. APLNR was observed in the granulosa cells, in the large luteal cells, in the secreting cells of the ampulla, in the uterus epithelial lining and uterine glands. The transcripts for APLN and APLNR were evidenced in all organ tissues examined. The highest level of APLN mRNA was detected in the Group 2 ewes in the luteal phase of the ovarian cycle compared to Group 1 ewes in the anestrous one. The relative content of APLN transcript was respectively twofold higher in the ovary (P