Elevation of brain manganese in calcium-deficient rats.

Rats, 3 weeks of age, consumed diets low or normal in calcium (Ca) with or without supplemental manganese (Mn) as Mn (II) acetate in drinking water. After 6 weeks, the animals were killed and [Mn] was determined in 8 brain regions, spinal cord, liver, serum, kidney, femur, and skeletal muscle. Serum [Mn] increased 1.5-, 4-, and 40-fold respectively, in normal Ca-supplemented Mn rats, low Ca rats, and low Ca-supplemented Mn rats. Elevation of tissue [Mn] occurred in all experimental groups with the greatest changes in the low Ca-extra Mn group: 6 - 12 fold in brain and spinal cord, and 2.5 - 140 fold in muscle, liver, kidney, and femur. Ratios of serum [Mn]/tissue [Mn] decreased as serum [Mn] increased suggesting saturable distribution. The findings suggest that Ca deficiency may cause Mn neurotoxicity by increasing dietary Mn absorption and brain [Mn].