Methods for long-term or permanent disruption of reproductive function via nonsurgical techniques are needed for a variety of species, including companion animals. In a previous study, we demonstrated the ability of a cytotoxin (pokeweed antiviral protein-PAP) conjugated to d-Lys6-GnRH, to disrupt reproductive function in adult male dogs. The objective of the present study was to examine the ability of a d-Lys6-GnRH-PAP conjugate to disrupt reproductive function in peripubertal male dogs. Peripubertal male dogs (n = 15; approximately 16-32 weeks old) were treated with d-Lys6-GnRH-PAP as follows: dogs (n = 7; Group I) received GnRH-PAP (0.1 mg/kg SQ) with a second treatment (0.25 mg/kg) 20 weeks later. An additional group (n = 3; Group II) of peripubertal dogs was treated with GnRH-PAP (0.25 mg/kg) twice (20 weeks apart). Control dogs (n = 5) received d-Lys6-GnRH analog (0.0045 mg/kg SQ) without PAP. Efficacy was assessed by monitoring testis size, serum concentrations of testosterone and LH, as well as LH release subsequent to a GnRH (5 μg/kg) stimulus. Dogs in Group I (n = 5) that did not respond to the initial two treatments were given a third GnRH-PAP injection (0.25 mg/kg), 12 months after the initial treatment. The initial GnRH-PAP treatment in peripubertal male dogs did not affect testis growth, LH release or serum testosterone concentrations; however, administration of a higher dose of GnRH-PAP after puberty resulted in a marked and rapid decline in testis size, serum testosterone concentrations and LH responsiveness to GnRH stimulation in 9 of 10 dogs. Suppression of reproductive function was maintained in treated dogs for 18-50 weeks; four dogs had suppression of reproductive activity through the end of the study. In conclusion, GnRH-PAP given after puberty markedly suppressed reproductive activity. Due to variability in the response and duration of suppression after treatment with GnRH-PAP, more research is required to determine its efficacy for nonsurgical sterilization of the male dog.
|Number of pages||9|
|State||Published - Sep 1 2006|
Bibliographical noteFunding Information:
Supported by the Kenneth A. Scott Charitable Trust and the Geraldine R. Dodge Foundation. The authors thank Dr. Heidi Ball, Coralie Munro, Matthew Allen, Latisha Burnaugh, Andrea Brum, Josh Boone and Amy Jensen for their assistance with these experiments.
Copyright 2008 Elsevier B.V., All rights reserved.
- Male dog
ASJC Scopus subject areas
- Small Animals
- Food Animals
- Animal Science and Zoology