The effect of antifreeze glycopeptides on membrane potential changes at hypothermic temperatures

The research on antifreeze glycopeptides (AFGPs) from Antarctic and Arctic fishes has focused primarily on their interaction with ice crystals. This study reports results of experiments in which pig oocytes, known to be sensitive to hypothermic temperatures, were exposed to 4°C for various periods of time, in solutions of different molecular weight AFGPs from Antarctic nototheniid fishes. The membrane potential was measured across the oolemma following hypothermic exposure. The results show that a physiological combination of the different molecular weight AFGPs protects the structural integrity of the oolemma and inhibits ion leakage across the oolemma at hypothermic temperatures. The results also show that the hypothermic protection is nonlinearly dependent on concentration and that separately, the different molecular weight glycopeptides do not stop ion leakage even at very high concentration. The protection of membranes at hypothermic temperatures is a new property of AFGPs which was not known prior to our work.