Evidence for dietary essentiality of lithium in the rat.

The purpose of this study was to determine the dietary essentiality of lithium (Li) in rats. In three experiments, two types of diets were fed during growth, reproduction, and lactation. In the first experiment, dams were maintained on a corn-based diet containing 2 ng or 500 ng (controls) Li/g through five successive periods of pregnancy and lactation. The offspring of dams fed the low-Li diet had significantly lower weaning weights (p = 0.011), and the percent weaned was lower (p = 0.094) than that of controls. In the second experiment, rats were maintained through three generations on a rice-based diet containing 0.6 ng Li/g, or the control (500 ng/g) diet. There was a significant effect of Li level on litter size (p = 0.017) and litter wt at birth (p = 0.006) in the third generation. The overall effect through three generations on litter wt at birth approaches statistical significance (p = 0.086). In the third experiment, third-generation rats were continued on the respective rice-based diets with three levels of dietary sodium, the normal level, one-half, and four times that level. The litter size and birth wt were significantly lower (p = 0.0030 and 0.0038, respectively) among the low-Li dams that consumed the normal and high-sodium levels compared to those that consumed the low-sodium diets. The interaction of Li and sodium as regards litter wt at birth approached significance (p = 0.083). Various tissues of the rats in the third experiment were analyzed for Li. It seems likely that Li exerts an essential nutrient role for the rat.