FERTILIZATION PROMOTING PEPTIDE, A TRIPEPTIDE SIMILAR TO THYROTROPIN-RELEASING-HORMONE, STIMULATES THE CAPACITATION AND FERTILIZING ABILITYOF HUMAN SPERMATOZOA IN-VITRO

Recent studies have demonstrated that a prostatic tripeptide similar i n structure to thyrotrophin-releasing hormone (TRH) can stimulate the in-vitro capacitation and fertilizing ability of epididymal mouse sper matozoa, Therefore we have proposed that this tripeptide be referred t o as fertilization promoting peptide (FPP), Using chlortetracycline fl uorescence analysis and the hamster oocyte penetration test (HOPT), we have obtained evidence that FPP can also promote the capacitation and fertilizing ability of ejaculated human spermatozoa in vitro. FPP (25 -200 nM) caused a significant increase in the proportion of B-pattern capacitated cells and a decrease in the proportion of F-pattern uncapa citated cells, with no significant stimulation of acrosomal exocytosis . Comparison of FPP with two structurally similar tripeptides, TRH and pyroglutamyl phenylalanylprolineamide, at 50 nh I revealed that only FPP could significantly promote capacitation, Finally, after a brief e xposure to progesterone to induce acrosomal exocytosis in capacitated cells, FPP-treated suspensions penetrated a significantly higher propo rtion of oocytes than the untreated controls when assessed in the HOPT . The presence of FPP in human seminal plasma at concentrations simila r to those used here suggests that, in vivo, FPP may play a positive r ole in promoting human sperm function.