Estrogen Flip-Flop
MCG researchers have found changes in blood vessel chemistry that may explain why estrogen goes from protecting women from heart disease to apparently increasing their risk later in life. Drs. Richard White and Scott A. Barman, MCG pharmacologists, found that estrogen targets nitric oxide synthase 1, one of three versions of the enzyme that makes the vasodilator, nitric oxide.
They then tried to block estrogen’s activity by blocking nitric oxide. “After we blocked nitric oxide production and added estrogen, we got a contraction,” Dr. Smith said. “Estrogen now had turned into a constrictor agent, an agent that would increase blood pressure.”
They looked further and found that normal aging decreases levels of the cofactors L-arginine and tetrahydrobiopterin, both critical to nitric oxide synthase’s production of nitric oxide. Instead of making nitric oxide, estrogen was producing the powerful age-promoting -- and apparently vasoconstricting -- oxygen-free radical, superoxide.
They are probing further to confirm their results, but the implications are significant, Dr. White said. “Estrogen is so powerful. We are looking with tunnel vision at its effect on blood pressure control. What would this do to bone? What would this do to Alzheimer’s? What happens to the brain is probably very similar. This could be a mechanism that would affect practically every system in the body.”