Albumin bound and alpha 2-macroglobulin bound zinc concentrations in the sera of healthy adults

Abstract

Reference ranges for albumin bound and alpha 2-macroglobulin bound zinc concentrations have been determined in a study of sera obtained from 134 healthy adults. The concentrations of zinc bound to alpha 2-macroglobulin were remarkably constant with a mean (+/-SD) of 2.4 +/- 0.6 mumol/l; the variations in total serum zinc concentrations were almost entirely accounted for by variations in the zinc associated with albumin. There were no sex related differences in the transport of zinc in serum; neither was this sensitive to the use of oral contraceptives. These data provide a baseline for further investigations into the effects of zinc deficiency on the serum transport of the metal.

PIP: The concentrations of albumin bound and alpha 2-macroglobulin bound zinc were investigated in the sera of 134 healthy human volunteers to provide control data for use in subsequent studies of zinc deficiency states. Whole blood was obtained from 86 men, aged 18-62 years, and 48 women, aged 19-60 years. 11 of the 48 women, aged 19-31 years, were taking combined oral contraceptives (OCs), 30 mcg ethinyl estradiol and 125-250 mcg levonorgestrel daily. Disposable plastic syringes and stainless steel needles were used to obtain venous blood, which was transferred to plain glass bottles which had been made zinc free by immersion in dilute nitric acid for 2 hours before being rinsed 6 times 6 times with deionized water and then dried. Serum was separated by centrifugation and stored in zinc-free polycarbonate tubes at -20 degrees Celsius until required for analysis. The summation of the concentrations of zinc found in association with albumin and alpha 2-macroglobulin were generally in good agreement with the total zinc concentration for each serum sample examined. The total recovery of zinc was 100.0 +or- 6.4% with a range of 88-114%. In percentage terms, the distribution of the recovered zinc was 16.3 +or- 4.1% (range 8.9-27.1%) with alpha -imacroglobulin and 83.7 +or- 4.1% (range 72.9-91.1%) with albumin. The molar ratios of albumin to albumin bound zinc and alpha 2-macroglobulin to alpha 2-macroglobulin bound zinc ere calculated each serum studied. Although the binding ratio between albumin and its associated zinc varied considerably, there was always a remarkable excess of albumin relative to zinc. Only 1.1-2.6% of the albumin present in the serum samples studied was engaged in zinc transport. The ratio of alpha 2-macroglobulin to alpha 2-macroglobulin bound zinc taken over the entire population was close to unity. No significant correlations were found between the concentrations of either albumin or alpha 2-macroglobulin and the concentrations of their associated zinc. The results arising from the analyses of the serum samples taken from the 11 women taking OCs were compared with similar data relating to 12 women, aged 40 years or less, who were not taking any drugs. There were no significant differences between these 2 populations for any of the parameters. The data provide a baseline for further investigations into the effects of zinc deficiency on the serum transport of the metal.