Factors affecting pentoxifylline stimulation of sperm kinematics in suspensions.

Sperm suspensions were prepared either by the 'swim-up' technique or by a Percoll gradient method before pentoxifylline was added to improve sperm motion characteristics. They were subsequently washed and then incubated with oocytes in in-vitro fertilization (IVF) programmes. The curvilinear velocity and lateral head displacement were approximately 20% higher in Percoll gradient-separated samples compared with samples prepared by the swim-up technique (P > 0.001), sperm motion characteristics being assessed by computer-assisted semen analysis. The dose-response study in which samples were separated by Percoll gradient/swim-up method showed that pentoxifylline gave maximum enhancement of sperm motion characteristics at a concentration of 2.8 mM/l, when the curvilinear velocity and lateral head displacement were significantly increased (P > 0.001). However, when pentoxifylline was removed by washing, the enhanced motion characteristics were reduced or lost in the process. Surprisingly, washing had a significant effect on the control samples, the motion characteristics being increased significantly (P > 0.001). This study casts doubt on the usefulness of pentoxifylline in IVF programmes.