Effect of a GnRH antagonist on anti-Müllerian hormone and follicular population in anestrous bitches

MARCHETTI, C; GRISOLIA-ROMERO, M, FAYA, M; PRIOTTO, M; GOBELLO, C; GOBELLO, C

Nantes

Simposio; 1st European Symposium on Animal Reproduction, 21st ? 23rd September 2023, Nantes, France; 2023

ESDAR, EVSSAR and ECAR (European Society for Domestic Animal Reproduction, European Veterinary Society for Small Animals Reproduction, European College of Animal Reproduction)

In female dogs, third-generation GnRH antagonists prevented ovulation, interrupted mid pregnancy and resolve pyometras. Anti-Müllerian hormone (AMH) is secreted by granulosa cells of small follicles of the ovary. The aim of this study was to describe the effect of the third-generation GnRH antagonist, acyline, on serum AMH concentrations and ovarian follicular population in late anestrous bitches. Four, 2.4 ± 0.4 y, 8.4 ± 0.9 kg beagle, late anestrous bitches were administered 330 μg/kg SC acyline every 10 days for 2 months and followed up for one additional month. Blood samples were drawn before (Day -1) and after (Days 15, 30, 45, 60, 75, and 90) the beginning of the treatment to measure AMH serum concentrations. The females were ovariectomized immediately after Day 90. The ovaries were histologically evaluated and total number of each follicle type was counted using the Gougeon and Chainy (1987) formula. AMH concentrations were grouped as pre (PRE), under (TREAT) and post (POST) treatment and compared by repeated measures ANOVA. None of the female dogs presented an estrous cycle during treatment. One bitch presented heat 20 days after treatment and corpora lutea. The total number of ovarian follicles was 96,200.10 ± 26,125.12, corresponding 84.13%, 11.36%, 7.8% and 0.01% to primordial, primary, secondary and antral structures, respectively. PRE AMH concentrations were 0.62 ± 0.17 ng/ml. AMH varied throughout the study period (P < 0.01), diminishing during TREAT to recover in the POST (0.2 ± 0.05 vs. 0.67 ± 0.22 ng/ml; P< 0.01). Acyline rapidly and reversibly diminished AMH concentrations evidencing the suppression and resumption of ovarian activity. The total number and proportion of follicles were similar to the ones previously reported for the species.