Neutrophil zinc: an indicator of zinc status in man

At present there is no single laboratory test which establishes the diagnosis of zinc deficiency in human subjects. Neutrophils are rich in zinc and have a short life span in the peripheral blood. The possibility that neutrophil zinc may be a reliable indicator of zinc status was tested in this study. Experiments were carried out in two groups of subjects. The first group of subjects included sickle cell anemia patients, known to be zinc-deficient. Zinc concentrations in the plasma, erythrocytes, and neutrophils were assayed by means of flameless atomic absorption spectrophotometry in 17 males and 7 females between the ages of 14-19 years. Neutrophil zinc in sickle cell anemia subjects correlated significantly with height (r = 0.62, p less than 0.005), weight (r = 0.66, p less than 0.001), and serum testosterone in males (r = 0.71, p less than 0.01). Inasmuch as growth retardation and hypogonadism in male sickle cell anemia patients have been related to a deficiency of zinc, these results indicate that the neutrophil zinc assay may be a good indicator of zinc deficiency in human subjects. Such correlations were not observed with zinc levels in the plasma erythrocytes. In the second experiment, a marginal deficiency of zinc was induced in five healthy human volunteers between the ages of 45-65 years by administering a semipurified soy protein-based diet for 12 weeks with daily zinc intake of 14.3 +/- 1.01 mg according to previously published techniques. Zinc balance (excluding sweat loss) on the soy protein diet at the end of the experiment was negative (-2.39 +/- 0.79 mg/dl). At the end of 4 weeks on the experimental diet, neutrophil zinc (mean +/- S.D.) was 107 +/- 27.2 in comparison to the base line level of 135.33 +/- 3.54 micrograms/10(10) cells (p less than 0.05). Changes in plasma zinc at the end of 4 weeks of dietary treatment were not statistically significant. After 12 weeks on the experimental diet, the neutrophil zinc declined 30.87%. In conclusion, our studies in two human zinc-deficient models suggest that neutrophil zinc levels may be a reliable and sensitive indicator of zinc status.