Expression of GnRH receptor in the canine corpus luteum, and luteal function following deslorelin acetate-induced puberty delay.

Contents The goals of this study were as follows: (Experiment 1) to examine the basic capability of canine corpora lutea (CL) to respond to GnRH by assessing expression of gonadotropin-releasing hormone receptor ( GnRH-R) in luteal samples collected throughout the luteal lifespan from non-pregnant dogs, and (Experiment 2) to investigate the effects of pre-pubertal application of the GnRH agonist deslorelin acetate on luteal function following the first oestrus. Mature CL were collected during the mid-luteal phase (days 30-45) from treated and control bitches. Transcript levels of several factors were determined: estrogen receptors ( ESR1/ERα, ESR2/ERβ ), progesterone (P4)-receptor ( PGR), prolactin receptor ( PRLR), PGE2-synthase ( PTGES) and PGE2 receptors ( PTGER2/EP2, PTGER4/EP4), vascular endothelial growth factor ( VEGFA) and VEGF receptors ( VEGFR1 and VEGFR2), cyclooxygenase 2 ( COX2/PTGS2), steroidogenic acute regulatory protein ( STAR) and 3β-hydroxysteroid dehydrogenase (3βHSD). Additionally, levels of Kisspeptin 1 ( Kiss1) and its receptor ( KISS1-R) were evaluated. Although generally low, GnRH-R expression was time dependent and was elevated during early dioestrus, with a significant decrease towards luteal regression. In deslorelin-treated and control dogs, its expression was either low or frequently below the detection limit. EP2 and VEGFR1 were higher in the treated group, which could be caused by a feedback mechanism after long-term suppression of reproductive activity. Despite large individual variations, 3βHSD was higher in the deslorelin-treated group. This, along with unchanged STAR expression, was apparently not mirrored in increased luteal functionality, because similar P4 levels were detected in both groups. Finally, the deslorelin-mediated long-term delay of puberty does not have negative carry-over effects on subsequent ovarian functionality in bitches. [ABSTRACT FROM AUTHOR]