MATERNAL, PLACENTAL AND CORD ZINC COMPONENTS IN HEALTHY WOMEN WITH DIFFERENT LEVELS OF SERUM ZINC

Serum zinc is known to decrease during pregnancy, but the range of ind ividual values at the end of normal gestation may be considerably larg e, with uncertain physiological significance in terms of maternal zinc status and maternal-fetal transfer of zinc. In this study we compared several maternal and cord blood indices of zinc status, placental zin c, placental metallothionein and the relationship between maternal, co rd and placental components, in 40 healthy pregnant women at delivery with different levels of serum zinc, Subjects were divided into three groups according to serum zinc using as cutoff points the lower and up per quartile values [LZn, <7.6 mu mol/l (n = 10); MZn, 7.6-10.7 mu mol /l (n = 20), and HZn, >10.7 mu mol/l (n = 10)]. Habitual zinc intakes were similar in all groups (average 11.5 mg/day). Considering all wome n, maternal serum and erythrocyte zinc correlated significantly (r = 0 .40; p = 0.021), Maternal erythrocyte zinc was higher (p < 0.01) in HZ n compared to the other groups. Maternal and cord values of serum zinc correlated significantly (r = 0.43; p = 0.006). Cord serum zinc value s were very similar in LZn and MZn but were higher (p < 0.01) in HZn. Cord erythrocyte zinc levels were similar in all groups and about 20-2 5% of the maternal values. Cord erythrocyte metallothionein levels wer e also similar in all groups and similar to maternal values. Comparing the percentage distribution of zinc in maternal and cord serum fracti ons, major differences were observed in HZn, with zinc in albumin frac tion bring 70% in cord compared to 56% in maternal serum. There was a higher (p < 0.01) percentage of zinc bound to alpha(2)-macroglobulin f raction in maternal serum of HZn compared to maternal serum of the oth er groups. Maternal and cord zinc in the albumin fractions correlated significantly (r = 0.48: p = 0.002) particularly in HZn (r=0.71; p < 0 .021). Placental zinc correlated negatively (r = -0.34; p = 0.035) wit h zinc in the maternal alpha(2)-macroglobulin fraction, but did not re late to placental metallothionein, which had similar levels in all gro ups (average 0.28 nmol/g wet tissue). Placental zinc levels were lower (p < 0.01) in HZn. Our results indicate that high levels of maternal serum zinc in healthy women at delivery may be related to maternal tis sue zinc redistribution that could favor diffusional components of mat ernal-fetal transfer of zinc.