Development of Rabbit Preimplantation Embryos under Thermal Stress in Vitro

The aim of our study was to examine the influence of short-term (6h) hyperthermia (41.5 °C and 42.5 °C) on the developmental capacity of preimplantation rabbit embryos in vitro. Rabbit embryos were isolated from superovulated and inseminated rabbit females after slaughter by flushing from oviducts of 19 hpc. The embryos were cultured in k-DMEM medium with the addition of 10 % fetal calf serum. In each experiment morula stage embryos were divided to hyperthermia (HT) and control group (C). Embryos from HT group were cultured at 41.5 °C or 42.5 °C for 6 hours and then post-cultured at 37.5 °C for 20 h. Control embryos were cultured at 37.5 °C. Then the embryos were evaluated for developmental stages and parts of the embryos were analyzed for the detection of Hsp 70 proteins. It was observed that rabbit embryos were able to resist against hyperthermia at 41.5 °C and the development to the blastocyst stage was not negatively influenced. These embryos showed the presence of protective Hsp 70 proteins as a reaction on thermal stress. Oppositely, hyperthermia at 42.5 °C significantly altered embryo development, which resulted in complete developmental arrest of embryos at lower developmental stages, whilst not a single embryo developed to expanded or hatching blastocyst stage. The presence of Hsp 70 proteins in these embryos was not confirmed. These results demonstrate a threshold of thermotolerance of preimplantation rabbit embryos to thermal stress in vitro and support hypothesis about protective role of Hsp proteins in embryo thermotolerance.