Effects of zinc deficiency on lead toxicity in rats

The effect of zinc deficiency on the toxicity of dietary lead in rats, as measured by body weight changes, tissue lead retention, and choice behavior in a complex maze was studied. Weanling rats were fed a zinc-free semipurified diet which was supplemented via drinking solutions with either 2 or 20 ppm zinc and 0, 10, or 100 ppm lead. During exposure, choice behavior was quantified in a radial maze. After a 3-week period on diet, the animals' physical development was assessed, and the retention of lead and zinc in bone and brain were determined by atomic absorption spectroscopy. Zinc deficiency slowed rats' weight gain, did not affect relative organ weights, increased the retention of lead in both calvarium and in brain, and reduced the accuracy of performance in the maze. Lead exposure at 100 ppm reduced body weight and increased relative organ weights, and reduced maze accuracy at both 10 and 100 ppm. Neither treatment affected the rats' running speed through the maze. Lead exposure and zinc deficiency exerted additive effects on body weight. The two treatments did not interact in the behavioral assay.