Free radicals in liberal amounts.

Free radicals in liberal amounts

When an arterial clot obstructs blood flow to the heart, doctors may dissolve it with enzymes, bypass it through surgery or stretch the artery with a balloon. But reentering blood may both rescue and damage the heart. The blood contains oxygen that is converted by certain cells into free radicals, highly reactive molecules that can disrupt DNA, cripple enzymes, poke holes in cell membranes and kill cells. Besides the heart, other organs--including the kidneys, lungs and brain--may become free-radical victims.

Although several studies have demonstrated free radicals' destructiveness (SN: 9/12/87, p.169), none has identified precisely which cells produce them. Scientists have proposed endothelial cells as one source. Now, in the June PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol.85, No.11), Jay Zweier, Periannan Kuppusamy and Gerard Lutty of Johns Hopkins University School of Medicine in Baltimore confirm that theory by reporting they have detected oxygen free-radical production in endothelial cells from cow arteries.

To measure free radicals, Zweier irradiated the cells with microwaves while exposing them to a varying magnetic field, a technique called electron paramagnetic resonance. The strength of magnetic field at which the cells absorb the microwaves indicates the types of oxygen free radicals they contain. The researchers examined endothelial cells that had been deprived of oxygen for 45 minutes, then reoxygenated. "The free-radical concentration increased more than 100-fold" and killed the cells, says Zweier. In addition, when the scientists gave the cells the enzyme superoxide dismutase, it appeared to stop creation of the free radicals.

Although Zweier's group examined only animal cells, their work has clinical relevance since superoxide dismutase is thought to help prevent reoxygenation injury in humans.