Effects of fertilization promoting peptide, adenosine, and pentoxifylline on thawed human sperm

Fertilization promoting peptide (FPP) and adenosine were demonstrated to be potential modulators of sperm capacitation in mammals. Both FPP and adenosine, by modulating the adenylate cyclase (AC)/cAMP signaling pathway, elicit similar biphasic responses in mammalian sperm (i.e., stimulating capacitation and inhibiting spontaneous acrosome loss). Pentoxifylline, an artificial sperm stimulant, is clinically used to enhance motility of sperm from infertile men. By inhibiting phosphodiesterase, pentoxifylline increases the intracellular cAMP level of sperm, and thus contributes to capacitation, hyperactivation, and acrosome reaction in animal studies. The effects of FPP, adenosine, and pentoxifylline on thawed human sperm are stressed. Chlortetracycline (CTC) fluorescence assessment revealed that none of the 3 reagents improved fertilization ability of post-thawed sperm. Motility studies with computer-aided sperm analyzer (CASA) showed significantly smaller STR (straight-line velocity) and LIN (linearity) in the FPP-treated group at 4 h of incubation (p ≦.005), significantly larger VCL in the adenosine-treated group (p ≦.05), and significantly larger VCL (curvilinear velocity) and smaller LIN in the pentoxifylline-treated group (p ≦.05). Significant decreases in percentage motility were also noted in both FPP and adenosine-treated groups (p ≦.05). It would appear that FPP potentiates fertilizing ability and prevents spontaneous acrosome loss, via regulating membrane-bound Na ⁺ -K ⁺ ATPase, and/or Ca ²⁺ ATPase, by keeping the sperm intracellular Ca ²⁺ concentration within the physiological range optimal for fertilization.