Dietary protein and lead retention.

The effects of dietary protein content on lead retention were studied in young rats. In experiments lasting between 3 and 6 weeks, rats given diets containing lead and 20% casein were fed ad libitum or were pair fed with rats given diets containing 6.5 or 7.5% casein. Among rats given 20% casein, lead retention was inversely related to growth rate. A reduction of dietary protein either had no effect or reduced lead retention. In other experiments lasting 4 days and using 203Pb, given orally or intraperitoneally, the recovery of isotope in the gutfree carcass was unaffected or reduced by a reduction in dietary protein. Blood and liver lead often increased when kidney and carcass lead decreased in response to a reduction of dietary protein. Conflicting observations on the effect of low-protein diets on lead retention may thus be due to opposing effects of low dietary protein and decreases of growth rate and to different responses of different tissues.