A cautionary note on the determination of forward motility protein activity with bovine epididymal spermatozoa

The effects of two compounds, Prosil 28 and poly G-L (a copolymer of D-glutamic acid and D-lysine), on apparent forward motility induction in bovine caput epididymal spermatozoa were examined. In a photographic forward motility assay, Prosil 28 and poly G-L both increased the apparent forward motility ofspermatozoa to 50-70% of the level achievable with bovine seminal plasma, a source of forward motility protein (FMP). An analysis of the time course and sperm velocity indicated the effects were due to the ability of the agents to prevent sperm from sticking to the glass surfaces of the assay chamber, as opposed to true motility induction. Since our previous data based on this assay failed to allow for this contribution to apparent forward motility, we have concluded that our previous measurements were at least 50% too high.