Zinc tolerance test patterns in normal children and in moderate and severe zinc deficiency states.

Twenty-six normal, 38 moderately and 14 severely zinc-deficient children, aged 2-12 years, were examined by clinical and laboratory approaches. After fasting-blood sampling, 120 mg zinc sulphate (25 mg elemental zinc) were administered orally to each group of children, to obtain zinc tolerance curve patterns. Sampling proceeded to the 2nd and 4th hours of the loading-test period. Plasma zinc was assessed on an atomic absorption spectrophotometer. In normal children, at the 2nd hour of loading, a significant (p < .001) elevation (1.764 +/- 0.133 mg/l) in the mean (+/- SEM) plasma zinc level was noted; also at the 4th hour a significant (p < .001) decrease (1.506 +/- 0.123 mg/l) in the mean plasma zinc level was shown. The mean plasma zinc level at the 4th hour was found higher than the mean fasting plasma zinc level (1.054 +/- 0.061 mg/l), but lower than the mean level found at the 2nd hour. In moderately zinc-deficient children, the rise in the 2nd hour and the fall in the 4th hour in the plasma zinc level were highly significant (p < .001 and p < .001, respectively) in relation to fasting blood level. However, in severely zinc-deficient children, the intensity of the increase (0.746 +/- 0.147 mg/l) in plasma zinc level at the 2nd hour was of lesser significance (p < .006) and the fall (0.424 +/- 0.061) mg/l) at the 4th hour was not significant. Therefore, in children with normal plasma zinc levels, an increase of more than 0.50 mg/l was seen at the 2nd hour of loading. This rise was seen to persist at the 4th hour. However, in children with moderate zinc deficiency, although again an increase of 0.50 mg/l was seen at the 2nd hour this increase did not persist at the 4th hour; and the 4th-hour value showed a significant decrease in relation to the 2nd hour value. Whereas, in children with severe zinc deficiency the rise of plasma level at the 2nd hour was less than 0.5 mg/l and the fall at the 4th hour was to such a level which was not significant in relation to fasting zinc level. This could be due to enhanced uptake of zinc off the circulation by the depleted tissues in severe zinc deficiency.