Abstract

Two-week's exposure to lead caused a three-fold rise in the number of total leucocytes per ?L blood in immature rats. Blood eosinophils, lymphocytes, monocytes and neutrophils increased significantly following lead exposure. There were no significant changes in band neutrophils. Of all leucocytes, eosinophils were the only cells that increased significantly in 24 h after estrogen treatment in lead-exposed animals. No changes in the remaining leucocytes were detected as a result of estrogen treatment in lead exposed or non-exposed rats. Previous work on 1-week exposure showed that lead only affected blood neutrophils. The difference may be explained as a result of time-dependent events, such as a change in regulatory mechanisms including the regulation of hormone receptor levels, or the synthesis of protective agents against toxicity such as stress proteins, which may play a role in hormone action.