Sex difference in free erythrocyte protoporphyrin (FEP) level. IV. Sex difference in FEP level in rabbits exposed to lead.

An experimental study on Japanese White (JW) rabbits was conducted to clarify the sex difference in FEP level. Male and female rabbits (n = 14 of each sex) were used. The animals of the same sex were divided into 3 groups; i.e., control group (5% glucose solution only, n = 4), low lead dose group (Pb 0.4 mg/kg.BW, n = 5) and high lead dose group (Pb 2 mg/kg.BW, n = 5). Lead was injected intravenously twice a week for 5 wk. The following parameters were determined once a week for 5 wk: blood lead (Pb-B), FEP, Ht, Hb, erythrocyte ALA-D activity, erythrocyte pyrimidine 5'-nucleotidase (P5N), urinary coproporphyrin (CP-U), urinary delta-aminolevulinic acid (ALA-U), iron in serum (Fe-S), and serum GOT and GTP. Average levels of FEP in female rabbits were higher than those in males between the 1st and 3rd week after the lead injection in the low lead dose groups, and in the final week in the high lead dose groups. In the periods without lead injection, the average levels of FEP in the female groups were not significantly higher than the corresponding levels in the male groups in every week except in the first week in the control. However, the mean of FEP levels in all female rabbits without Pb treatment was higher than that in male rabbits (t-test). By the analysis of variance for the gains of FEP from the initial value, only the low lead dose group showed a significant sex difference (female > male); that is, the female group tended to increase when compared with the male group. Furthermore, the week when FEP began to increase in the female groups was earlier than that in the male groups in the low lead dose group. In the high lead dose group, both sexes reacted to the lead exposure from the same early week. As for the parameters of anemia, the average levels of Ht and Hb tended to be lower in females than in males, but Fe-S levels were not affected by lead in both sexes and no consistent sex difference could be observed. By lead exposure, ALA-D and P5N were inhibited, and ALA-U was increased, but these parameters showed no evident sex difference. The average levels of CP-U tended to be higher in females than in males in the administration of low lead dose and to be inversely higher in males than in females in the administration of high lead dose.(ABSTRACT TRUNCATED AT 400 WORDS)