Use of urinary biomarkers of ovarian function in the chinchilla: a comparative study of two ovulation induction protocols.

PONZIO M.F

Toronto

Congreso; International Society of Wildlife Endocrinologists Annual Meeting.; 2011

Toronto Zoo

Intensive hunting for fur placed chinchilla populations at the brink of extinction (IUCN critically endangered and Appendix I of CITES). A hybrid of the two chinchilla taxa has been bred for fur production, providing a unique model to develop procedures that could be applied to their endangered counterparts. However, a key aspect for the implementation of captive breeding programs is the study of the species’ reproductive physiology. Attempts to obtain repeated blood samples from chinchillas were unsuccessful because of small vein size and their stress-susceptible nature. Therefore, non-invasive techniques provided a unique opportunity, allowing long-term endocrine monitoring. The objective of this study was to use urinary biomarkers of ovarian function to assess two protocols for exogenous regulation of the hypothalamus-hypophyseal-gonadal axis. Females were induced using eCG alone (Novormon, Syntex, 30 I.U., n=6) or GnRH (Gonasyn, Syntex, lecirelin acetate 0.2 mL, n=4). Hormones assessed in 24 h urine longitudinal samples before and after injection included creatinine (colorimetric assay from creatinine standard set, Sigma #C3613), pregnanediol glucuronide (PdG, C. Munro R13904), estrone conjugate (EC, C. Munro R522-2), LH and FSH (NIDDK-anti rat LH-RIA-S118rabbit AFPC697071P; NIDDK-anti rat FSH-RIA-11 AFP-C0972881, National Hormone & Peptide Program, CA, USA). Comparative profiles of progesterone (P) and estradiol (E) metabolites (I125 RIA kits, Coat-A-Count, Siemens) and the occurrence of vaginal opening (as external sign of oestrus) were also determined. After eCG injection, vaginal opening was observed after 4 ± 0.6 days in 93.1 % of the females. Elevation of urinary PdG and EC metabolites above baseline occurred after 8 and 10 days respectively, reaching values of 2720 ± 1109.8 and 22.5 ± 9.7 ng/mg creatinine. Ovarian stimulation using GnRH resulted in less pronounced peaks of hormonal activity, indicating a lower response to the treatment (PdG: 1463 ± 620.8 EC: 19.5 ± 6.7 ng/mg creatinine). Vaginal opening occurred after 3.1 ± 0.9 days in 76.9 % of the females. Similar profiles were obtained using E or P determinations, yet metabolite concentrations were significantly lower. Occurrence of LH and FSH activity peaks were variable among individuals. These data provide promising results for manipulating the cycle in female chinchillas, a first step towards establishment of a protocol for assisted reproduction.