Yuriy Kirichok of the University of California, San Francisco, explains that sperm in the male reproductive tract have to rest easy -- not moving their "tails" or flagella -- lest they wear themselves out prematurely and give up any chance of ever finding an egg.
Scientists have long known that sperm's activity level depends on their internal pH, but Kirichok and colleagues found the channel that allows the tiny cells to rid themselves of protons.
Once in the female reproductive tract, that proton release changes their internal environment from acidic to alkaline and begins their race to the finish line, Kirichok says.
Kirichok says there are many conditions that open up the Hv1 pore, including alkaline conditions and the removal of zinc outside the cell. They also open when exposed to the endocannabinoid known as anandamide, a substance present in both the male and female reproductive tracts.
Endocannabinoids are natural lipids that influence the activity of neurons that act on the same receptors that the active component of marijuana does. It remains to be shown, but that connection might explain why marijuana has been linked to impaired male fertility.
"Marijuana likely activates sperm prematurely, leaving them (burned) out in a matter of hours," Kirichok said in a statement.
The findings are published in the journal Cell.