A simple spectrophotometric method of assay of forward motility of goat spermatozoa.

Spermatozoa from the cauda epididymidis were suspended in modified Ringer solution containing 2% Ficoll and 50 microliters were placed at the bottom of a standard optical cuvette containing 1.3 ml modified Ringer. This amount was just sufficient to cover the entire width of the light beam. Vigorously motile spermatozoa that moved upwards into the light beam were registered continuously as an increase of absorbance at 545 nm with a spectrophotometer equipped with a recorder. The first slope of the curve represents an index of the velocity of the population of cells showing the fastest motility. When measured in this system forward motility activity (expressed as units) increased linearly with cell concentration. Ficoll at concentrations of 1-5% had no effect on the values recorded but 250 microM-p-chloromercuribenzoic acid completely inhibited motility. The spectrophotometric values did not necessarily correlate with light microscope assessments of forward motility, because the former method provides an assessment of numbers of motile cells and their rate of progression.