Brazilian Journal of Medical and Biological Research
On-line version ISSN 1414-431X
GOULART, E.C. et al. Effects of lead and/or zinc exposure during the second stage of rapid postnatal brain growth on delta-aminolevulinate dehydratase and negative geotaxis of suckling rats. Braz J Med Biol Res [online]. 2001, vol.34, n.6, pp. 785-790. ISSN 1414-431X. http://dx.doi.org/10.1590/S0100-879X2001000600014.
Lead has been shown to produce cognitive and motor deficits in young rats that could be mediated, at least in part, by inhibition of the zinc-containing heme biosynthetic enzyme d-aminolevulinate dehydratase (ALA-D). In the present study we investigated the effects of lead and/or zinc treatment during the second stage of rapid postnatal brain development on brain, kidney and blood ALA-D specific activity, as well as the negative geotaxis behavior of rats. Eight-day-old Wistar rats were injected intraperitoneally with saline, lead acetate (8 mg/kg) and/or zinc chloride (2 mg/kg) daily for five consecutive days. Twenty-four hours after treatment, ALA-D activity was determined in the absence and presence of DL-dithiothreitol (DTT). The negative geotaxis behavior was assessed in 9- to 13-day-old rats. Treatment with lead and/or zinc did not affect body, brain or kidney weights or brain- or kidney-to-body weight ratios of the animals. In spite of the absence of effect of any treatment on ALA-D specific activity in brain, kidney and blood, the reactivation index with DTT was higher in the groups treated with lead or lead + zinc than in the control group, in brain, kidney and blood (mean ± SEM; brain: 33.33 ± 4.34, 38.90 ± 8.24, 13.67 ± 3.41; kidney: 33.50 ± 2.97, 37.60 ± 2.67, 15.80 ± 2.66; blood: 63.95 ± 3.73, 56.43 ± 5.93, 31.07 ± 4.61, respectively, N = 9-11). The negative geotaxis response behavior was not affected by lead and/or zinc treatment. The results indicate that lead and/or zinc treatment during the second stage of rapid postnatal brain growth affected ALA-D, but zinc was not sufficient to protect the enzyme from the effects of lead in brain, kidney and blood.
Keywords : lead acetate; zinc chloride; delta-aminolevulinate dehydratase; negative geotaxis; postnatal brain growth.