The action of small doses of lead on erythrocyte D-aminolevulinic acid dehydratase in the mouse.

After a single intraperitoneal administration of lead in very small doses [1--100 micrograms Pbac/kg body weight (bw)], there was a dose-dependent, highly significant inhibition of erythrocyte D-aminolevulinic acid dehydratase (D-ALA-D) activity in mice. The maximal inhibition occurred between 3 and 24 h post injection (p.i.). After that, a rapid recovery of the D-ALA-D activity took place so that four days after lead administration, enzyme activity exceeded even the normal value. Only after eight days p.i. did the D-ALA-D value return to the initial level after a biphasic course. After 10 i.p. injections of 0.1 to 10 micrograms Pbac/kg bw, there was again a dose-dependent, highly significant inhibition of the erythrocyte D-ALA-D activity in mice. The maximal inhibition was shown to be 24 h after the last lead injection. In contrast to the single i.p. administration, however, we found a monophasic course for the return of D-ALA-D activity. The D-ALA-D values did not exceed the normal range at any time after 10 i.p. lead injections. Ten and 30 days oral administration of lead corresponding to i.p. doses exhibited similar results in D-ALA-D inhibition.