Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2002
Publication Date: 1/1/2003
Citation: Crichton, E.G., Bedows, E., Miller-Lindholm, A., Baldwin, D.M., Armstrong, D.L., Graham, L.H., Ford, J.J., Gjorret, J.O., Hyttel, P., Pope, C.E. 2003. The efficacy of porcine gonadotropins for repeated stimulation of ovarian activity for oocyte retrieval and in vitro embryo production and cryopreservation in siberian tigers (panthera tigris altaica). Biology of Reproduction. V. 68(1). 105-113. Interpretive Summary: Stimulation of growth of ovarian follicles with exogenous gonadotrophins is a common method to increase number of ova that are available for fertilization. This technique is used with animals of great value or uniqueness. At the request of staff at the Henry Doorly Zoo, plasma samples from tigers that had received one to three superovulation protocols of exogenous porcine gonadotrophins were evaluated for the presence of antibodies against porcine gonadotrophins. All tigers tested negative for antibodies against porcine FSH and LH. We conclude that tigers do not form antibodies rapidly after injection with exogenous porcine gonadotrophins. This contrasts data in house cats in which use of equine chorionic gonadotrophins for induction of superovulation readily stimulates production of antibodies that cross-react with porcine gonadotrophins. These findings are valuable to individuals who are attempting to propagate endangered species through superovulation.
Technical Abstract: Initial studies suggested that Siberian tiger gonadotropins are more homologous with those of porcine than any other commercially available preparation. Therefore the present study measured the efficacy of repeated ovarian stimulation with purified porcine gonadotropins on the follicular, hormonal and immunogenic responses in Siberian tigers. In addition, the ability of oocytes retrieved by laparoscopic follicular aspiration to fertilize and cleave in vitro was evaluated. Controlled rate and vitrification cryopreservation methods were also compared for their ability to support ongoing cleavage following thawing of presumptive tiger embryos generated in vitro. Vitrification supported continued embryonic cleavage in vitro while controlled rate freezing did not. Stereological microscopy indicated an excellent ovarian response with the recovery of quality cumulus-oocyte complexes that apparently fertilized and cleaved in vitro. However, closer examination of the results at the ultrastructural and physiological levels revealed abnormal and unnatural responses such as the failure of cumulus-oocyte complexes to reach maturity and hormone levels to approach normalcy. At the same time, analyses of blood for antibodies failed to detect an immune reaction to these foreign gonadotropins in an assay that tested positive for the pLH-challenged domestic cat. Together, these observations indicate that while the use of porcine hormones for ovarian stimulation in the Siberian tiger has value, some limitations to the approach still exist. These data support research in progress to develop homologous gonadotropins for assisted reproduction efforts in endangered felids.