Influence of sex hormones on free erythrocyte protoporphyrin response to lead in rats.

Following oral administration of lead a difference in free erythrocyte protoporphyrin (FEP) increase was found between adult male, adult female and suckling rats: young animals are more susceptible than adult female rats which in turn exhibit a greater FEP increase than adult male animals. This observation parallels that made previously in humans. Possible difference in iron metabolism does not appear to explain the sex-linked difference in FEP response to lead. Sex hormones mainly progesterone, seem to play a role but their interaction with lead on the FEP response is restricted to female rats and apparently is not mediated through changes in delta-aminolevulinic acid synthetase activity.