Thursday, February 18, 2010

New discovery about sperm's ability to swim

Scientists have found the trigger that gets sperm swimming in the female reproductive tract.

Sperm cells in the testis are pretty quiet . . . they don't seem very interested in swimming.  However, after they are ejaculated into the female reproductive tract they become activated and get with the program. We already knew that the sperm cells need to raise their pH in order to kick into their swimming mode . . . but we didn't know how that is actually done.

In an article in the journal Cell, researchers report that they have the answer . . . one-way proton (H+) channels called Hv1 that open when sperm enter the female reproductive tract.  Increasing the intracellular pH triggers the influx of calcium ions, which in turn activate the sperm flagellum.  And they're off!

The increase in intracellular sperm pH also enables the sperm's acrosome to become activated and get ready to do its job, too.

Hv1 may be a key to triggering the hyperactivation and capacitation of sperm necessary for male fertility.

The researchers also found that a chemical similar to the active ingredient in marijuana inhibits the Hv1 channels and thus reduced fertility.  Perhaps this explains low fertility among males who are chronic users of marijuana.  And perhaps this opens the door to discovering chemicals that can be used to regulate the sperm fertility.

Want to know more?
Science News web edition : Thursday, February 4th, 2010
[Summary article includes a cool fluorescent micrograph.]

Acid extrusion from human spermatozoa is mediated by flagellar voltage-gated proton channel. 
Lishko, P.V. et al.
Cell Volume 140, Issue 3, 327-337, 5 February 2010
[Original research article with some fabulous images in the graphical abstract and an excellent movie that features the scientists explaining their discovery. ]


Alex said...

Thanks for another great article. One thing that got me thinking was the fact that in the Intro to the paper the authors say that sperm cytoplasmic pH is about 6.5. Then in the Science News article they state that: "The concentration of protons inside a sperm is roughly 1,000 times higher than outside." So I when take these 2 statements together I infer that the sperm are being activated in an environment with a pH of about 9.5. Since vaginal pH is on the acidic side this doesn't seem to make sense to me. Maybe I'm missing something here.

Kevin Patton said...

Alex, I hadn't caught that one. Although the paper's intro states <6.5, digging a bit deeper it looks they are starting at something near pH 5.5 and saw up to two units of pH change . . . a total factor of about 100 (not 1,000). The "thousand times" figure comes from a quote rather than directly from the article and I suspect that either the quoted researcher misspoke during and interview, or the reporter made the error, or there is something neither of us is seeing clearly.

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