MANGANESE DEPRIVATION AFFECTS RESPONSE TO NICKEL DEPRIVATION

A study was performed to ascertain whether manganese deprivation would alter the response of rats to nickel deprivation and thereby provide some clues as to the biochemical function of nickel in higher animals. A 2 x 2 factorially arranged experiment was performed with groups of nine weanling Sprague-Dawley rats. The basal-dried skim milk, acid-was hed ground corn diet contained 12 ng Ni/g and 100 ng Mn/g. The experim ental variables were supplemental nickel at 0 and 1 mu g/g and supplem ental manganese at 0 and 20 mu g/g. After being fed the diets for 10 w eeks, the rats exhibited numerous changes indicating that manganese st atus affected the response to nickel deprivation, and vice versa. More over, nickel affected several variables associated with the functional roles of manganese. These types of effects were prominent in variable s associated with the metabolism of arginine. For example, nickel depr ivation increased the amount of arginase present in liver that was act ivated in vitro by manganese or nickel; with the manganese-stimulated activity, the increase was enhanced by manganese deprivation. Manganes e deprivation alone did not affect the amount of manganese- or nickel- stimulated arginase, which is surprising because arginase is a mangane se-containing enzyme. Both nickel and manganese deprivation decreased blood urea nitrogen; the lowest value occurred in rats fed the diet de ficient in both elements. An interaction between manganese and nickel also affected plasma creatinine concentration; the highest value was i n rats fed the diet supplemented with both elements. An interaction be tween manganese and nickel affected soft tissue calcium concentration. In skeletal muscle and kidney, nickel deprivation decreased calcium w hen manganese was supplemented, but increased calcium when manganese w as deficient; just the opposite occurred in heart. The findings sugges t that nickel has a biochemical role closely associated with the metab olism of arginine. (C) 1995 Wiley-Liss, Inc.