A group of researchers from Stanford have identified the nitric oxide gas as the chemical incitement for a cascade of chemical events gradually resulting in the development of an embryo.He says,it begins with the build-up of nitric oxide gas inside the sperm.
The research is based on the sex lives of male and female sea urchins - spiny, purple invertebrates found in the Pacific Ocean just a few yards from Epel's laboratory on California's Monterey Bay. Experiments reveal that normal sea urchin sperm contains an enzyme called nitric oxide synthase, which remains inactive until a few seconds before fertilisation.
"As the sperm approaches the egg," notes Epel, "the enzyme quickly produces large amounts of nitric oxide gas, which is injected into the egg once the sperm and the egg make contact."The injection of nitric oxide gas from the sperm triggers the release of calcium inside the egg about 30 seconds later.
Calcium then activates nitric oxide synthase already present in the egg, producing more nitric oxide gas, which in turn causes the release of more calcium throughout the egg. In the 1970s, Epel and other researchers showed that calcium is the essential factor that sparks development in eggs. As calcium levels rise, metabolic changes occur that cause the egg to divide and form into an embryo.
Sea urchins have long served as a model for understanding fertilisation in other living beings, including people because sperm and eggs are relatively easy to extract from them.
If nitric oxide is involved in mammalian fertilisation, Epel, says that it could be useful in genetic engineering, cloning and in vitro fertilisation.
Not to be confused with nitrous oxide, or 'laughing gas', nitric oxide plays an important role in human physiology. It maintains blood pressure and flow by keeping our blood vessels open - a significant discovery for cardiologists as well as for the manufacturers of the impotence drug, Viagra. It also functions as an important neurotransmitter in people and is used by white blood cells to kill tumors, bacteria and other invaders.