Endocrine effects of the GnRH antagonist, acyline, in domestic dogs

VALIENTE C, GARCÍA ROMERO G, CORRADA Y, BLANCO PG, DE LA SOTA PE, GOBELLO C.

Conferencia; Latin American Veterinary Conference (LAVC).; 2009

INTRODUCTION Gonadotrophin realizing hormone (GnRH) antagonists have a potential clinical utility in hormone dependent diseases, contraception and in vitro fertilization protocols in dogs. They competitively block and inhibit GnRH leading to immediate pituitary suppression. OBJETIVE To describe the effect of a single dose of the new, 3rd generation GnRH antagonist, acyline, on serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) in male dogs. MATERIALS AND METHODS Animals & Procedures: Five reproductively normal mixed-bred dogs were randomly assigned to one of the following treatment groups: ? ACY: acyline (NIH, USA) 330 ug/kg sc (n=3) ? PLB: placebo group (n=2) -Blood samples were drawn the day before treatment (Day -1) and then 30, 60 and 90 min, 3, 6, 9, 12 and 24 hours, and 3, 6, 9, 14, 22 and 29 days thereafter for the determination of FSH (Biocode®, Belgium), LH (Biocode®, Belgium), and T (DPC®, USA) serum concentrations. Statistical Analysis -pre-treatment (Day -1) values between ACY and PLB groups ( T test) -Postreatment hormones´ responses (summary measures) RESULTS AND DISCUSSION ? Pretreatment hormone values did not differ between ACY and PLB groups (FSH se p= 0.97, LH p= 0.79 and T p=0.2). ? Concentrations of the 3 hormones progressively decreased to nadir values (Fig. 1,2 and 3) ? On Day 14, serum concentrations of the 3 hormones began to increase throughout the remaining study period (Fig. 4) ? On Day 29, hormonal concentrations were not different to pretreatment values (FSH p= 0.28; LH p = 0.53; T p = 0.77). ? In the PLB group it was not possible to describe a period of maximal suppression. -Detailed knowledge of these endocrine effects will greatly improve their practical use before GnRH antagonists could be widely recommended. -In conclusion, in male dogs, a single dose of the GnRH antagonist, acyline, safely and reversibly decreased serum concentrations of FSH, LH, and T for 9 days with no detectable side effects.