22 June 1998

New Compounds Stop Sperm's Assault On Egg

Contraception can be thought of as a struggle between allied forces trying to protect the chastity of an egg against an invasionary force of sperm. One defence tactic used is the spermicide which, while successful in eliminating the enemy sperm, also kills off the allied forces stationed in the area. Currently available spermicides act by shearing off the cellular membrane of the sperm. Without this protective coat the sperm cannot move or function and consequently die. This process is unselective (a bit like saturation bombing), and it frequently kills many vaginal cells that are needed for protection against invading bacteria and STDs. However a group of researchers at the Wayne Hughes Institute in Roseville, Minnesota have discovered a possible new spermicide that acts like a sniper, selectively eliminating the sperm, and leaving the allied vaginal cells intact.

Reported in the June issue of Biology of Reproduction, the Minnesota researchers have found a way to protect the egg from the sperm using compounds based on the element vanadium. The compounds rapidly and irreversibly stop sperm cells by interfering with the 'motors' that power them. The sperm are immobilized and die shortly after.

The researchers, Osmond D'Cruz, Phalguni Ghosh, and Fatih M. Uckun, made several vanadium compounds and added them to active human sperm. All of the sperm in the assay were immobilized within 60 seconds of exposure to the compounds, and nearly 60 per cent were dead after 12 hours. Importantly, the vanadium-exposed sperm had intact acrosomal membranes indicating that an end to casualties from 'friendly fire' may be just around the corner.

Nicole Kresge, Scripps Institute