Vitamin E and the Peroxidizability of Erythrocyte Membranes in Neonates

Abstract

We showed the increased susceptibility of neonatal biomembranes to oxidation by a kinetic analysis using an azo compound as a free-radical initiator and red blood cell (RBC) ghosts as a model membrane. When the RBC ghosts were oxidized, oxygen consumption was suppressed during the induction period in which membrane tocopherol was consumed at a constant rate, while increased oxygen uptake was observed after the tocopherol was exhausted. The total tocopherol content was similar in cord, maternal, and adult RBC ghosts, and there were no differences in the induction period (t/_inh) among the three types of ghosts. While the oxygen uptake rate during the induction period (R_inh) was similar in cord and adult ghosts, the rate in the subsequent phase (R_p) was considerably faster in the cord ghosts. Fatty acid analysis in the membrane lipids showed that the active bisallylic hydrogen (active H) content was greater in cord ghosts than in adult ghosts. The active H content closely correlated with the R_p, but did not with the R_inh. The kinetic chain length (KCL), i.e., the ratio of the rate of propagation to that of initiation, was calculated from R_p and tocopherol consumption rate and KCL values were higher in cord ghosts than in adult ghosts. The faster R_p and the higher KCL of the cord ghosts were attributable to a greater active H content rather than to the tocopherol content.

Key Words:

• Red blood cell ghosts
• neonates
• polyunsaturated fatty acids
• active bisallylic hydrogen atoms
• α-tocopherol
• azo compounds
• oxygen uptake
• induction period
• kinetic chain length
• peroxidizability
• hemolysis