EFFECT OF ANTIFREEZE PROTEINS ON THE MOTILITY OF RAM SPERMATOZOA

The effect of the antifreeze peptide type I (AFP) from Winter flounder , Pseudopleuronectes americanus, and the antifreeze glycoprotein (AFGP ) from Antarctic cod, Dissostichus mawsoni, was assessed on the motili ty of ram spermatozoa (Dorset and Dorset x Romney) after chilling (5 d egrees C) and after freeze-thawing. During chilling, spermatozoal moti lity decreased significantly at an AFP or AFGP concentration of 0.1 mu g/ml and at concentrations above 10 mu g/ml (P < 0.05). Thus, at 5 de grees C these antifreeze proteins can have a mildly cytotoxic effect a t certain concentrations. Addition of AFP or AFGP to the freezing medi um at concentrations of 0.1 to 10 mu g/ml significantly reduced the lo ss in spermatozoal motility that occurs due to the freeze-thaw process (P < 0.001). The effect was not concentration dependent nor did it de pend on which antifreeze protein was added. However, due to the cytoto xicity during the chilling stage, only AFP at a concentration of 10 mu g/ml increased the percentage of motile spermatozoa significantly fol lowing freezing and thawing over that of the control (P < 0.05). Mecha nisms to explain the effect of these proteins on spermatozoal motility after chilling and after freeze-thawing are proposed. (C) 1993 Academ ic Press, Inc.