Non-protein bound zinc concentration in human plasma and amniotic fluid measured by ultrafiltration.
Using an ultrafiltration technique, apparent non-protein bound (NPB) zinc concentrations in plasma were found to be 2.2 +/- 0.2 (SEM) microgram Zn/l (10 observations) in normal males, 1.6 +/- 0.3 (10) micrograms/l in normal females and 1.2 +/- 0.2 (10) micrograms/l in pregnant mothers during their 16th week of gestation. These values are about 0.2% of the total plasma zinc concentrations, at least five-fold less than previous estimates. In amniotic fluid, the NPB-zinc concentration was 12.6 +/- 0.4 (10) micrograms/l, 5-10 times that of normal plasma, though the total zinc concentration (100 +/- 30 micrograms/l) was only one tenth that of plasma. When plasma or amniotic fluid samples were ultrafiltered without precaution against CO2 loss, their NPB-zinc concentrations increased, suggesting that pH changes alter zinc binding. The low concentration of NPB-zinc in plasma explains the low urinary excretion of zinc observed by others and would be expected to restrict the entry of zinc into cells.
D000328:Adult; D000653:Amniotic Fluid / Q000032:analysis*; D000925:Anticoagulants; D005260:Female; D005615:Freezing; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D011247:Pregnancy; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D013048:Specimen Handling; D014462:Ultrafiltration / Q000295:instrumentation; D015032:Zinc / Q000032:analysis* / Q000097:blood
D000925:Anticoagulants; D012709:Serum Albumin; D015032:Zinc