Determination of zinc in serum and urine by atomic absorption spectrophotometry; Relationship between serum levels of zinc and proteins in 104 normal subjects

Abstract

Serum and urine zinc were measured by atomic absorption spectrophotometry. The drift in base-line was continuously registered and corrections for the drift were made in the calculations of zinc measurements to avoid any adjustment in the instrument settings. Food intake was shown to lower the serum zinc concentration by 19% on average ( p < 0.001). A diurnal variation of serum zinc was observed with a minimum at 7 p.m. Venous stasis elevated the mean serum zinc concentration by 13% ( p < 0.001) and the mean serum protein level by 14% ( p < 0.001). Weak correlations between serum zinc and both the serum concentration of proteins and of albumin were found in 104 normal subjects. There was no correlation between serum concentrations of zinc and α 2-macroglobulin. The concentration of serum zinc was 9% higher in males than in females ( p < 0.005) which was not explained by sex differences in serum protein concentrations. Furthermore, males had a higher excretion rate of zinc in urine than females, when expressed as μmol Zn/24 hour ( p < 0.01). This difference disappeared when urine zinc was corrected to urinary excretion rate of creatinine. Our results show that blood samples for serum zinc measurement should be taken in the morning in fasting state. The urinary zinc excretion rate should be related to the creatinine excretion rate to avoid sex differences.