Oxidative Damage during a 10‐ to 12‐d Saturation Dive

Abstract

The NASA Extreme Environment Mission Operations (NEEMO) underwater habitat is a useful spaceflight analog. The increased air pressure in the habitat exposes crew members to higher oxygen pressures, which increase their risk for oxidative damage to DNA, proteins, and lipids. DNA oxidation occurs at an increased level, similar to that observed in smokers and astronauts returning from space. Astronauts in space and NEEMO crew members also have changes in iron metabolism. Newly formed red blood cells are destroyed and body iron stores are elevated. Excess iron can act as an oxidant and cause tissue damage. In this study we investigated aspects of oxidative damage and tested whether toxic forms of iron were present when iron stores increased during NEEMO missions. Subjects (n = 12) participated in 10‐ to 12‐d saturation dives, and blood and 24‐h urine samples were collected twice before, twice during, and twice after the dive. During the dive, ferritin was significantly (P < 0.001) higher, transferrin tended to be lower (P = 0.053), and transferrin receptors were lower (P < 0.001). Total homocysteine was significantly (P < 0.001) elevated and superoxide dismutase activity was decreased (P < 0.05). Labile plasma iron was measurable during the dive but not before or after it. These data indicate that the NEEMO environment increases iron stores, which may cause oxidative damage. This study was supported by the NASA Human Research Program.