Effect of exposure to low level lead on growth and growth hormone release in rats.

This study was undertaken to examine the effect of exposure to low level lead on growth and growth hormone (GH) release. Female pups exposed to lead beginning in utero were smaller than controls on postnatal day 7 (P = 0.06). There was no corresponding effect in males. No overall differences in body weights were detected in either sex with respect to treatment effect. No differences in food or water intake were observed at any time. Pituitaries from 49-day-old lead-treated pups responded to in vitro incubation with growth hormone releasing factor (GRF) with a smaller increase in GH release than those from control pups (P = 0.08). In the case of the dams, lead did not affect body weight, body length, food consumption or pituitary responsiveness; however, water consumption was significantly increased in the lactating dam (P < 0.05). Interestingly, blood lead content in 5-day-old pups (43.3 +/- 2.7 micrograms/dl) exposed to lead in utero was more than twice that of their 49-day-old litter-mates (18.9 +/- 0.7 micrograms/dl). At 49 days blood lead levels in female pups (19.94 +/- 0.8 micrograms/dl) were significantly higher than those of male pups (17.00 +/- 1.1 micrograms/dl). Maternal blood lead levels on the same day averaged 22.7 +/- 2.5 micrograms/dl. This study suggests that exposure to a low level of lead can reduce pituitary responsiveness to a hypothalamic stimulus. In addition, the data reinforce the importance of considering age and sex when evaluating the toxic effects of lead.