The influence of low lead doses on the reticulo-endothelial system and leucocytes of mice.

The half-life of the indian ink elimination (carbon clearance method) was used as a measure of the RES activity. A significant increase of the RES activity in mice was found already after a single intraperitoneal (i.p.) administration of 20, 50, or 100 micrograms PbAc/kg body weight (b.w.). A significant RES stimulation could also be demonstrated after a single or 10-day oral administration of lead at doses of 10-1,000 micrograms PbAc/kg b.w. No RES stimulation occurred, however, after 30-day oral administration of lead. On determining the reactivity of the RES to 1 microgram endotoxin/kg b.w. it was found that it was already limited after a single and 10-day oral lead administration. After 30-day oral administration of lead (doses 10-1,000 micrograms PbAc/kg b.w.) the reactivity of the RES was completely suppressed. After a single and 10-day oral administration of lead (doses 10-1,000 micrograms PbAc/kg b.w.) we observed a marked leucocytosis. This effect was most clearly seen after a dose of 100 micrograms PbAc/kg b.w.; the leucocyte counts were increased by up to 50% in comparison with controls. After 30-day oral administration of lead, such a leucocytosis was no longer detectable. In accordance with the findings on the RES, the leucocytosis that is normally induced in the animals by 1 microgram endotoxin/kg b.w. was significantly reduced or completely suppressed both after single and also after 10 and 30 days' oral administration of lead at doses of 100 and 1,000 micrograms PbAc/kg b.w. These results show that the resistance state of the mouse is impaired already by low doses of lead.