Changes in erythrocyte properties during the first hours of life: electron spin resonance of reacting sulfydryl groups

In an attempt to clarify the mechanism by which the red cells (RBC) of newborn infants are protected against oxidative agents, electron spin resonance (ESR) assays were carried out using the nitroxide radical 4-maleimide-2,2,6,6-tetramethylpiperidinyl-l-oxyl (Mal-6), a sulfydryl-reacting agent. The ESR assays were performed in 24 samples of cord blood, 20 samples of blood from 4-day-old infants, and eight samples of 8-h-old infants. The analyses were carried out on whole blood and washed erythrocytes were resuspended in buffered saline. The same experiments were performed in 10 blood samples from healthy adults as controls. Whole blood, before and after removing the buffy coat, and cell-free plasma were also examined by ESR assay. Cell-free plasma and buffy coats proved not to be appreciably involved in the Mal-6 behavior. The data of the ESR spectroscopy demonstrated a significantly slower reaction rate in the samples of cord blood and in blood of 8-h-old infants, compared to that of 4-day-old infants and adults. No significant differences in Mal-6 behavior could be detected between cord blood and 4-day-old infant blood in the results of ESR assays performed in washed red cells. Chemical determination of RBC-reacting sulfydryl groups and the assays of glutathione also demonstrated the absence of differences between cord blood and blood of 4-day-old infants. The results of our investigation suggest that the RBC-sulfydryl-reacting groups are less involved in the detoxification of oxidative agents during the first hours of life than in the following days. This peculiarity of RBC of younger infants appears to be due, to a considerable extent, to the modulation by plasma factors of the interactions between Mal-6 and RBC-reacting sulfydryl groups. Therefore, the changes in plasma components occurring during the first hours of life appear to modify the interactions between the RBC and the oxidative agents. © 1988 International Pediatric Research Foundation, Inc.