Expression of GnRH receptor in canine corpus luteum,
and luteal function following deslorelin-induced puberty delay
D Kaya*, A Gram*, S Aslan, S Schäfer-Somi, M Kuru, MP Kowalewski
(*) contributed equally
Background
GnRH modulates both inhibitory and stimulatory responses affecting ovarian function in dogs and other mammals
The inhibitory actions of GnRH or its agonists (GnRH-
a) on gonadal steroidogenesis involve suppression of
gonadotropin receptors or mediator enzymes
involved in steroidogenic pathways.
Background
In dogs, the steroidogenic activity of CL seems to be controlled at the level of the substrate supply and/or turn over.
Expression of the two major factors involved in
synthesis of P4, i.e., 3βHSD and STAR protein, was
well investigated in canine CL during the course of
dioestrus in both non-pregnant and pregnant
animals
(Kowalewski et al. 2009 and 2013).
Background
…the mechanisms of suppression and resumption of ovarian activity and, subsequently, luteal function
after short/long- term inhibition of gonadal activity
remains poorly understood.
Aim
to investigate the presence and expression
levels of factors involved in luteal activity, as well
as the expression of GnRH and GnRH-R in the
canine luteal tissue following the first estrus
after long-term prepubertal GnRH agonist-
deslorelin treatment.
Material
Pre-pubertal
•Deslorelin implant (Suprelorin®, 9,4 and 4,7 mg) treated; n=4
(supression period: 72.7 – 84.0 weeks, Kaya et al., 2015)
•Control (Placebo); n=4 Non-pregnant diestrus
•During luteal phase (5-65 d)
at days: 5, 15, 25, 35, 45 and 65 after ovulation (n=3-5 per group)
Methods
Estrus cycles
-vaginal cytology - blood sampling
CL samples from deslorelin-treated and control bitches (OHE during the mid-luteal phase; days 30-45)
CL samples from non-pregnant bitches throughout
dioestrus (R-OHE)
Methods
Hormone analysis (ECLIA)
- P4 and E2
Real-Time PCR
- mRNA expression profiles
GnRH-R, ERα, ERβ, PGR, PRLR, PTGES and PGE2 receptors (EP2 and EP4), VEGFA and VEGF receptors (VEGFR1 and -2), COX2, STAR protein and 3βHSD, Kiss1 and its receptor)
Localization (GnRH-R) - in situ hybridization
Pre-pubertal
Non- pregnant diestrus
The mean length of the proestrus was 8.5±5.06 and 8.7±4.3 days in deslorelin-treated and in control bitches, respectively.
Cytological examinations showed that there was no delay in the transition period from proestrus to estrus in treated group compared with the control.
Results
Distribution of E2 and P4
Results
P>0.05
PTGES and EP2 expression in CL following first estrus
Relative mRNA expression
P = 0.200 P = 0.043
Results
*
**
ER alpha and ER beta expression in CL following first estrus
Results
Relative mRNA expression Relative mRNA expression
P = 0.078 P = 0.198
PGR and StAR protein expression in CL following first estrus
Relative mRNA expression
Results
P = 0.095
3βHSD and COX2 expression in CL following first estrus
Relative mRNA expression P = 0.629*
**
Results
Kiss1-R and PRL-R expression in CL following first estrus
Results
Relative mRNA expression
P = 0.343 P = 0.224
GnRH-R expression in CL during diestrus.
a
Relative mRNA expression b
ab ab
ab
Results
P<0.001
Localization of GnRH-R in CL during early diestrus in situ hybridization
Results
A similar GnRH-R expression pattern was observed for both treated and control animals. It was low or frequently below the detection limit.
GnRH- gene expression determined in deslorelin treated and control group was n=1/4 and n=1/4, respectively (positive versus negative).
Results
P<0.001
the results from our study indicate that long-term delay of puberty with GnRH analogue-deslorelin does not have carry-over-effects on subsequent estrus activity and luteal functionality in bitches.
Conclusion
Thank you for your attention!..
My sincere thanks to:
Prof.Dr. Mariusz P. Kowalewski and
colleagues from the Vetsuisse Faculty Zurich
