NAD+ and NADH in brain cortex from mice exposed to high oxygen pressure

Abstract

Experiments were done in vivo to determine the effect of oxygen at high pressure (OHP) on NAD+ and NADH in mouse brain cortex. A 7% decrease (N.S.) in NADH was found in brain cortex from mice exposed to 6 atm of 100% oxygen for 8 min, while a 20% decrease (P less than 0.01) in cortical NADH, when compared to controls, occurred when mice were exposed to this oxygen pressure for either 16 min or 48 min. A 20% decrease (P less than 0.05) in cortical NADH was also observed in mice which had been killed during hyperactivity (a state preceding convulsions), at seizure onset, or 10 s post-convulsions. No measurable change in cortical NAD+ was observed at any of these oxygen exposure times or stages of toxicity. When mice were exposed to either 3.5 atm or 6 atm of oxygen for 16 min, a statistically significant decrease in cortical NADH (P less than 0.01) coupled with an increase in the NAD+/NADH ratio was found only at 3.5 atm and 6 atm, and not at 1 atm. The decrease in cortical NADH and increase in the NAD+/NADH ratio were reversed when mice were decompressed and exposed to air for 30 min. Disulfiram, a drug found to delay the onset of oxygen seizures, did not prevent the oxygen-induced decrease in cerebral NADH or increase in the NAD+/NADH ratio. The decrease in cortical NADH in mice exposed to OHP did not correlate with the onset of oxygen-induced convulsions.