Abstract
The effects of dietary protein levels (10% and 20%) on changes in the activity of serum alkaline phosphatase (APase, E.C. 3.1.3.1) and zinc concentrations in the serum and femur of zinc-deficient rats were determined using a demineralized soybean protein isolate as the source of dietary protein. When rats were fed a diet containing 10ppm zinc, body weight gain and food intake were higher in the 20% protein (HP) group than in the 10% protein (LP) group. However, serum APase activity, and serum and femur zinc concentrations were lower in the HP group than in the LP group. Similar tendencies were observed in rats fed a protein diet containing 4ppm zinc. The rates of reduction of these parameters in zinc-deficient rats during the feeding period were higher in the HP group than in the LP group. Rats fed the LP-zinc-deficient diet survived longer than those fed the HP-zinc-deficient diet. These results suggest that the higher rate of reduction of serum APase activity and serum and femur zinc concentrations in rats fed the HP-zinc-deficient diet might be due to an increased zinc requirement in the body.
