Dietary arginine, silicon and their interaction affect bone composition and T-lymphocyte mitogenic response of rats

Abstract

Both silicon (Si) and arginine (Arg) affect collagen formation. In a previous experiment, Arg supplementation increased the concentration of Si in plasma. Thus, the following experiment was designed to determine if dietary Arg would alter the utilization of Si. Male weanling Sprague-Dawley rats were assigned to groups of 12 in a 2 × 2 factorially arranged experiment. Supplemented to a ground corn/casein basal diet containing 1.2 μg Si were Si as sodium meta-silicate at 0 and 35 μg/g and Arg at 0 and 5 mg/g diet. The rats were fed ad libitum deionized water and their respective diets for nine weeks. Con-A induced DNA synthesis of splenic T-lymphocytes was determined. Mineral concentrations of organs and plasma were determined by inductively coupled argon plasma atomic emission spectrometry. Body weight, liver weight/body weight ratio and plasma Si were decreased, and plasma alkaline phosphatase activity was increased by Si deprivation. Femoral calcium, copper, potassium and zinc concentrations were decreased, whereas manganese concentration was increased, by Si deprivation. Arg supplementation decreased femoral concentrations of Si but increased femoral manganese. DNA, germanium and sodium concentrations of the femur were affected by an interaction between Si and Arg; the concentrations were decreased by Si deprivation in femurs of those animals not fed supplemental Arg. Vertebral concentrations of phosphorus, sodium, potassium, copper, manganese and zinc were decreased in Si-deprived animals. The vertebral concentration of iron was decreased by Si deprivation in animals not fed supplemental Arg, whereas Si was decreased by Si deprivation in animals fed supplemental Arg. Arg supplementation increased vertebral concentrations of sodium, potassium, manganese, zinc and iron. An interaction between Si and Arg affected the Con-A induced DNA synthesis of splenic T-lymphocytes. In Si-supplemented animals, Arg supplementation significantly reduced DNA synthesis of splenic T-lymphocytes. This indicates that dietary Si alters the effects of Arg on T-lymphocyte proliferation. The findings of altered femoral and vertebral mineral concentrations support the contention that Si promotes bone formation.