Sex Difference of Free Erythrocyte Protoporphyrin (FEP) in Humans and Rats

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Several biological parameters of lead exposure and iron deficiency anemia, such as FEP, <delta> -aminolevulinic acid dehydratase (ALA-D), Serum iron (FeS), Ht, Hb etc, were measured for 98 women and 59 men (both 51 <-!+> 11 years old) lived in rural districts.Women showed a higher FEP level than men; 63.0 <-!+> 19.4 in women and 54.6 <-!+> 21.2 <mu> g/dl・pcv in men. Women Pb-B level showed a lower tendency than in men. Ht, Hb and FeS were also lower in women than in men. There was no difference in ALA-D activity between both sexes.Correlations between these biological parameters were calculated, and no significant correlations were observed between Pb-B and these parameters. There were a little correlations between Ht, Hb and FEP for FeS.In rats injected lead (0.5 mg Pb/kg・BWX6) and the control, FEP level was lower in female than in male, and the same pattern was observed in urinary <delta> -aminolevulinic acid (ALA-U). In high lead dose group (5 mg Pb/kg.BWX6), urinary coproporphyrin (CP-U) was lower in female than in male.In another study with castrated male rats, estradiol (50, 250 <mu> g/kg・BWX22) was injected into the rats with or without lead (5 mg Pb/kg.BWX6). No significant increase due to estradiol was observed in FEP, ALA-U and CP-U in both rats with or without lead, while a decrease in Ht and body weight by estradiol was shown.These results suggest that the increase of FEP in human females is not caused by sex hormone, and mainly caused by tendency of iron deficiency anemia induced by blood loss (i.e. menses, pregnancy, delivery etc) and the differences of dietary habits (quality and quantity of food etc).