Effect of acute zinc depletion on zinc homeostasis and plasma zinc kinetics in men

Abstract

The kinetic analysis with a compartmental model suggests that the profound decrease in plasma zinc concentrations after 5 wk of severe zinc depletion was mainly due to a decrease in the rate of zinc release from the most slowly turning over body zinc pool.

Zinc exposure for female workers in a galvanizing plant in Northern Italy

“…Our results are therefore consistent with the hypothesis that the respiratory tract is able to absorb zinc following inhalation [1,14,16,17,20,21,24,29,40]. In this regard, both experimental and field studies suggest that zinc and zinc oxide are efficiently adsorbed by airborne dusts [45,46]: impacting upper airways, 35% to 80% of zinc-enriched particles would be retained, swallowed and eventually absorbed through the gastrointestinal tract, the absorption rate of which would depend on the nutritional status, ranging between 8% and 80% [1,14,16,17,20,21,31,45]. As environmental sampling identified an airborne concentration of 1.58±0.34 mg/m 3 for dusts having aerodynamic diameter < 10 μm, a significant role for this exposure route may therefore be supposed.…”

“…On the one hand, mean white blood cell count was within the normality range, and no significant correlation was identified with serum or urinary levels of zinc, ultimately ruling out an acute inflammatory effect elicited by airborne zinc and zinc compounds [11][12][13]28,30]. On the other hand, hemoglobin concentrations were in the normality range for Italian female population, implying no significant effect on the iron metabolism, as suggested by previous studies on high exposure settings [16,17,20,21,31,42,43]. However, as the mean seniority of the sample was relatively high (i.e., 10.4±3.4 years), it is possible that our results may be somehow affected by a significant "survivor bias."…”

“…In other words, even the relatively low amount of zinc absorbed through both respiratory and gastrointestinal system in a setting of reduced occupational exposure may eventually result in transient high serum zinc concentration, that elicits an increased urinary excretion in order to avoid an excessive increase of body stores. Unfortunately, there is no clear correlation between absorbed dose and excreted amount of zinc: its rate is dependent on both current and past intakes, probably in dynamic equilibrium with body stores [20,21,[24][25][26][27]. However, several limitations within our study should be addressed.…”

“…Following the absorption through the gastrointestinal tract, the highest concentrations have been found in bone, muscle, prostate, liver and kidneys [15][16][17]. Liver, pancreas, bone, kidney and muscle are the major tissue storage sites, and less than 10% of the body's total zinc, equivalent to a 10-18 μM concentration, is readily exchanged with plasma [18][19][20][21]. Under normal physiological conditions, blood zinc is chiefly localized within erythrocytes, and the plasma/ serum zinc level is around 100 μg/dl: the available research has recently identified -in 80-160 μg/dl -the normal reference values for Italian non-occupationally-exposed subjects whereas previously estimated values had suggested a range of 81.2±13.1 μg/dl for general Italian population (75.5±12.3 μg/dl in female subjects) [22,23].…”

“…Around 98% of serum zinc is bound to proteins (in particular: 85% to albumin, 12% to α 2 -macroglobulin) whereas the remainder 2% is bound to ultrafiltereable small organic molecules such as citrate and amino-acids. As the latter is only excreted in the urine, usual urinary levels range from 25 μg/dl to 65 μg/dl (or 0.5 mg/g creatinine) [20,21,[24][25][26][27]. Toxicokinetics of inhaled zinc still remains largely undefined.…”