Sperm’s swimming secrets revealed

Updated: Feb 05, 2010, 00:00 AM IST

Washington: In a breakthrough study, scientists from University of California, San Francisco, have identified a mechanism that prompts the male sperm to start swimming to reach and fertilize egg.

The research has led to the discovery of new target for male contraception.

The sperm’s motility is short lived. When in the male reproductive tract they have to rest easy, 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. They have found a channel that allows the tiny cells to rid themselves of protons.

Lead researcher Yuriy Kirichok likens the quiescent sperm cells to balloons inflated with protons instead of air.

"The concentration of protons inside the [sperm] cell is 1,000 times higher than outside. If you just open a pore, protons will go outside. We identify the molecule that lets them out,” Kirichok said.

Once in the female reproductive tract, that proton release changes their internal environment and begins their race to the finish line.

The newly discovered Hv1 protein channel may allow for new ways to modify the activity of sperm in either direction, Kirichok added.

Many key biochemical reactions in sperm depend on intracellular pH levels, including its initial activation, hyperactivation once near the fallopian tubes and the acrosome reaction, in which enzymes are released to penetrate the egg.

"All of these events are essential to fertilization," Kirichok said.

"You can imagine now that we know the molecule responsible we could block it to prevent activation and fertilization as a kind of male contraception," Kirichok added.

The study appears in the journal Cell, a Cell Press publication.