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Vitamin E and the peroxidizability of erythrocyte membranes in neonates
Insights
Neonatal red blood cell (RBC) membranes show increased susceptibility to oxidation due to higher levels of active hydrogen in lipids. This contributes to faster oxidation rates and higher kinetic chain lengths in neonatal membranes compared to adult ones.
Area of Science:
- Biochemistry
- Membrane Biology
- Oxidative Stress
Background:
- Neonatal biomembranes are susceptible to oxidative damage.
- Tocopherol (vitamin E) is a key antioxidant in cell membranes.
Purpose of the Study:
- To investigate the kinetic differences in oxidation between neonatal and adult red blood cell (RBC) ghosts.
- To identify the factors contributing to altered membrane susceptibility to oxidation in neonates.
Main Methods:
- Kinetic analysis of red blood cell (RBC) ghosts using an azo compound as a free-radical initiator.
- Measurement of oxygen consumption and tocopherol levels during oxidation.
- Fatty acid analysis of membrane lipids to determine active bisallylic hydrogen content.
Main Results:
- Neonatal (cord) RBC ghosts exhibited a faster rate of oxygen uptake (Rp) and higher kinetic chain length (KCL) post-tocopherol exhaustion compared to adult ghosts.
- While total tocopherol content and induction period (tinh) were similar, neonatal ghosts had a greater content of active bisallylic hydrogen (active H) in membrane lipids.
- The increased active H content in neonatal membranes correlated with the faster propagation rate (Rp) and higher KCL.
Conclusions:
- Neonatal RBC membranes are more susceptible to oxidation due to a higher content of active hydrogen in their lipids, not differences in tocopherol levels.
- The greater active H content in neonatal membranes contributes to a faster propagation rate and higher kinetic chain length during oxidative stress.
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 (tinh) among the three types of ghosts. While the oxygen uptake rate during the induction period (Rinh) was similar in cord and adult ghosts, the rate in the subsequent phase (Rp) 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 Rp, but did not with the Rinh. The kinetic chain length (KCL), i.e., the ratio of the rate of propagation to that of initiation, was calculated from Rp and tocopherol consumption rate and KCL values were higher in cord ghosts than in adult ghosts. The faster Rp and the higher KCL of the cord ghosts were attributable to a greater active H content rather than to the tocopherol content.