Relationship between zinc parameters and either body weight gain, protein intake or survival time in zinc-deficient rats.

This study was undertaken to examine the relationships between zinc parameters (serum alkaline phosphatase activity, and zinc concentration in serum and femur) and either body weight gain, protein intake or survival time in zinc deficient rats. Demineralized soy protein (DP) and alkali-treated soy protein (AP) were used as dietary protein sources in order to make zinc deficient diets (< 0.5 mg zinc/kg diet). The same diets (DP and AP diets) supplemented with lysine or cystine were also given freely to rats. Moreover, in other experiments, the above relationships were examined. During the early stages, a significant negative correlation between body weight gain and survival time in zinc-deficient rats was demonstrated. The significant negative correlation coefficient between protein intake and survival time increased gradually, and the maximum value of this correlation coefficient was higher than that between body weight gain and survival time. The significant correlations between protein intake and femur zinc concentration were recognized throughout the longer periods. These results show that the number of zinc-deficient rats which survive decreases as protein intake increases throughout the feeding period, that the influence of protein intake is greater than that of body weight in early stages, and that the zinc requirements of rats rise with the increase in protein intake.