Effect of leucocytes on the hypoosmotic swelling test of human sperm

The hypoosmotic swelling test was used to evaluate the size of physiologically competent sperm after their exposure to the influence of leucocyte-derived superoxide anions. In sperm suspensions, preincubated in the presence of 50 x 10(4)mL-1 leucocytes capable of producing 0.93 +/- 0.63 nmol of O2- (range 0.21-2.03 nmol) over 30 min at 37 degrees C, a significant decrease in the percentage of swollen sperm compared to that in the control sperm suspensions without added leucocytes was found (p < .001, n = 46). Addition of phorbol myristate acetate, an activator of the release of O2-, further diminished the ability of hypoosmotic sperm tail swelling (p < .001), while superoxide dismutase inhibited this effect. This study suggests that even very low amounts of superoxide anions may influence the functional integrity of sperm. Therefore, any source of superoxide anion production should be eliminated and/or inhibited in sperm suspensions used in assisted reproduction techniques.