The acrosome reaction is a Ca(2+)-dependent exocytotic process that is a prerequisite step for fertilization. External calcium entry through voltage-activated Ca(2+)channels is known to be essential in inducing the acrosome reaction of mammalian spermatozoa. Due to their complex geometry, however, electrophysiological identification of sperm Ca(2+)channels has been limited. Here we identified Ca(2+)channel mRNAs expressed in motile human sperm using RT-PCR and their levels were compared using RNase protection assays. L-type, non- L-type, and T-type Ca(2+)channel mRNAs were detected by RT-PCR using degenerate primers. Cloning and sequencing of the PCR products revealed alpha1B, alpha1C, alpha1E, alpha1G, and alpha1H sequences. RT-PCR using specific primers repeatedly detected alpha1B, alpha1C, alpha1E, alpha1G, and alpha1H mRNAs, and additionally alpha1I mRNA. But alpha1A and alpha1D messages were not detected. Relative expression levels of the detected Ca(2+)channel subtypes were compared by RNase protection assays. The abundance of detected mRNA messages was in the following order: alpha1H> or =alpha1G> or =alpha1E> or =alpha1B>alpha1C>alpha1I. These findings indicated that human motile sperm express multiple voltage-activated Ca(2+)channel RNAs among which T-type and non-L-type channel messages are likely to be predominantly expressed. Based on their relative expression levels, we propose that not only T-type but also non-L-type calcium channels may be major gates for the external calcium influx, required for the acrosome reaction.
Calcium/*metabolism ; Calcium Channels/biosynthesis/classification/*genetics ; Human ; Male ; RNA, Messenger/*metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Spermatozoa/*metabolism

OBJECTIVETo identify the types of voltage-dependent Ca2+ channels (VDCCs) in human ejaculated sperm using molecular technology.

METHODSBased on the WHO criteria, the donated semen was screened by computer-aided sperm analysis (CASA), the sperm optimized by swim-up method, and the VDCCs' alpha1 subunits examined by reverse transcription polymerase chain reaction (RT-PCR).

RESULTSSuch mRNA messages as alpha1H, alpha1G, alpha1E, alpha1B and alpha1C were detected, but alpha1A and alpha1D were not.

CONCLUSIONHuman motile sperms express multiple VDCC RNAs, among which T-type and non-L-type channel messages are likely to be predominantly expressed. Not only T-type but also non-L-type calcium channels may be major gates for the external calcium influx, which helps regulate sperm motility and acrosome reaction.

Calcium ; metabolism ; Calcium Channels ; biosynthesis ; classification ; genetics ; Humans ; Image Processing, Computer-Assisted ; Male ; RNA, Messenger ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; Spermatozoa ; metabolism