Periódicos Brasileiros em Medicina Veterinária e Zootecnia

p. 750-755

Effect of cold stress on physicochemical characteristics and biological activity of equine chorionic gonadotropin

Alvarez, R. HNatal, F. L. NAlmeida, B. EOliveira, J. EBartolini, PMelo, A. J. FDuarte, K. M. RRibela, M. T. C

The purpose of this study was to evaluate iffreezing-thawing and cooling processes affect thestructural properties and biological activity ofcommercial equine chorionic gonadotropin (eCG). First,the structure profile of diluted eCG underwent none,one or three cycles of freezing-thawing was analysed byreverse phase high-performance liquid chromatography(RP-HPLC). In a second experiment, groups ofprepuberal rats were treated with sterile water forinjection USP or eCG that underwent none, one or threecycles of freezing-thawing to assess the increase ofovarian weigh. Finally, groups of prepubertal gilts weretreated with diluted eCG immediately afterreconstitution (T1), after refrigeration for six months(T2) and after freezing and subsequently thawing for one(T3) or three (T4) cycles. The control group (T5) receivedsterile water for injection USP without eCG. Ovulationwas induced with human chorionic gonadotropin (hCG),administered 72 h after the eCG. Gilts were slaughteredfive days after the hCG injection and ovaries wererecovered and analysed for the presence of corporalutea. Data were analysed by ANOVA and Fisher’sexact tests. In the analyses by RP-HPLC, the retentiontimes of cold stressed eCG were similar to unstressedcontrol. The mean ovarian weight of rats treated with coldstressed and unstressed eCG was statistically higher thanwater control (P < 0.05). Lastly, significantly more giltsovulated in groups T1, T2, T3 and T4 than in thecontrol T5 (P < 0.05). It was concluded that freezingthawing,as well as cooling over a period of up to sixmonths, did not significantly change the structuralproperties or biological activity of eCG.(AU)

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