Observation of the Incidence of Acrosome Reaction in Human Spermatozoa Treated with Mibefradil as a T-type Ca2+i Channels Inhibitor.

Lee,  Jae Ho; Lee,  In Sun; Kim,  Young Chan; Son,  Weon Young; Lee,  Jung Ha; Han,  Ching Tack

Original Article

Korean Journal of Fertility and Sterility 2000;27(1):9-14.
Published online January 1, 2001.

Observation of the Incidence of Acrosome Reaction in Human Spermatozoa Treated with Mibefradil as a T-type Ca2+i Channels Inhibitor.

Jae Ho Lee, In Sun Lee, Young Chan Kim, Weon Young Son, Jung Ha Lee, Ching Tack Han

Abstract

OBJECTIVE : The sperm acrosome reaction is a Ca2+ -dependent exocytotic event that is triggered by adhesion to the mammalian egg's zona pellucida. Previous studies suggested a role of Ca2+ channels in acrosome reactions. This study was conducted to investigate the T-type calcium channel is operated in acrosome reaction of human spermatozoa. METHOD : Human semen samples were obtained from healthy donors with nomal criteria. The spermatozoa were divided into five groups: Group 1 were non-treated as a control; Group 2 where spermatozoa were exposed to 5 micrometer Ca2+ A23187 (Ca2+i); Group 3 where spermatozoa were exposed 5 micrometer Ca2+i and mibefradil; Group 4 where spermatozoa were exposed 5 micrometer Ca2+i and nifedipine, and Group 5 where spermatozoa were treated with 5 micrometer Ca2+i and both of mibefradil and nifedipine. Spermatozoa in all groups were retrieved after incubation for 15 and 30 minutes at 37degrees C. After staining with PSA-FITC, fluorescence was observed under a fluorescence microscope, and AR was evaluated on a total >100 spermatozoa/side. RESULT AND CONCLUSION : We observed on acrosome reaction inhibition rate in human spermatozoa the various of concentration of mibefradil, nifedipine. Maximum response was noted with 1.0 micrometer mibefradil and the decrease of acrosome reaction inhibition rate 45%. Nifedipine in acrosome reaction inhibition rate was only about 25%. The Ca2+i-induced AR of spermatozoa was significantly suppressed by mibefradil. Incidence of the suppression was depending on concentration of mibefradil. Results from the present study suggest that the human spermatozoa possess T-type channel. The observation that reversible inhibitor of T channels in male germ cells provides a new mechanism of contraceptive action.