THE ROLE OF THERMAL HYSTERESIS PROTEINS DURING CYROPRESERVATION OF OOCYTES AND EMBRYOS

Recent studies on the short- and long-term preservation of oocytes and em certain proteins known as thermal hysteresis proteins (THPs) or '' antifreeze proteins'' (AFPs), can interact with the cell membrane and protect oocytes and embryos during exposure to cryogenic temperatures (-130-degrees-C to -196-degrees-C) and hypothermic (4-degrees-C) tempe ratures. The cryoprotective function is dependent on the concentration and type of THP used. During vitrification more than 40 mg/ml of such THPs is required; however, for successful cryopreservation using slow freezing or for short-term hypothermic storage (1-4- days), optimal c oncentrations are in the range of 0.1-1 mg/ml, depending on the type o f THP used. The ability of the THPs to interact with and stabilize the vitrification solution and the cell membrane, which is one of the pri mary sites of damage during cryopreservation, provides new opportuniti es for the cryopreservation of human and animal gametes.