Effect of glyceryl trinitrate on sperm motility and lipid peroxidation in normozoospermic men

The objective of this study was to assess the in-vitro effects of the nitric oxide substrate glyceryl trinitrate (GTN) on sperm motility and membrane lipid peroxidation. Nitric oxide (NO) can impair sperm motility, possibly by an alteration of cyclic nucleotide levels. NO may also be protective against lipid peroxidation. Semen samples from nine normospermic men were prepared by a swim-up technique. Each specimen was divided into four aliquots, one of which was the control sample. The other three had 10(-6), 10(-8) or 10(-10) M GTN added. Sperm motility was then analysed over 180 min using a Hamilton Thorn motility analyser. Lipid peroxidation was assessed by measuring media malondialdehyde (MDA) levels at 180 min. Compared with control, the following measurements were reduced (p < 0.05) over the first 60 min in the 10(-6) M GTN aliquots only: mean path velocity (reduced by 14-15%), curvilinear velocity (reduced by 12-21%), straight-line velocity (reduced by 18-19%) and percentage of hyperactivated spermatozoa (reduced by 38-43%). MDA levels and head movement parameters were comparable amongst all aliquots (p > 0.05). The depressant effects of GTN on sperm motility appeared to be transient and reversible. The effects observed may be due to NO generated by GTN, or to GTN itself. This suggests that NO may have a role in vivo as a physiological inhibitor of sperm motility. The addition of GTN did not appear either to cause sperm membrane damage or to protect the spermatozoa from lipid peroxidation.