Plasma and erythrocyte levels of trace elements and related antioxidant enzyme activities in low‐birthweight infants during the early postnatal period

Abstract

To discover the relationship between antioxidant enzyme activities and trace elements in low‐birthweight infants during the early postnatal period, we analysed catalase (CAT), CuZn‐superoxide dismutase (CuZn‐SOD) and glutathione peroxidase (GSH‐Px) activities in erythrocytes, and compared them with Fe, Cu, Zn and Se levels in plasma, and Cu, Zn and Se levels in erythrocytes until 16 wk after birth. Thirteen low‐birthweight infants whose mean birthweight and gestation were 1520 ± 293 g and 32.0 ± 2.8 wk were enrolled in this study. All infants were without chronic complications, well nourished, and predominantly fed standard formula or preterm formula based on cow's milk, commercially available in Japan. Cu and Zn levels in erythrocytes did not decline after birth, in contrast to a temporal decrease in plasma Zn. Erythrocyte CAT activity was significantly higher at 16 wk than that at birth or 4 wk of age. Erythrocyte CuZn‐SOD activity did not change throughout the study period. Only Se in plasma and erythrocytes decreased remarkably after birth, which resulted in a significant decline in erythrocyte GSH‐Px activity at 8 and 16 wk (11.2 ± 2.0 and 11.0 ± 1.1 U/g Hb) compared to that at birth (12.4 ± 2.1 U/g Hb). Conclusion: During the early postnatal period, erythrocyte CAT and CuZn‐SOD activities did not decrease in formula‐fed, low‐birthweight infants. Japanese commercial formula not supplemented with Se, however, caused postnatal plasma and erythrocyte Se deficiency and a concomitant decline in erythrocyte GSH‐Px activity in the same subjects.