Determination of zinc in erythrocytes, granulocytes and serum by flame atomic absorption spectrophotometry

Zinc and copper levels in premenstrual syndrome

OBJECTIVE

To determine whether changes in peripheral zinc and copper levels are associated with symptoms of premenstrual syndrome (PMS).

DESIGN

Ten PMS patients and 10 controls gave blood at 2- or 3-day intervals through three menstrual cycles. Serum zinc and copper were measured by flameless atomic absorption spectrophotometry.

RESULTS

In the controls zinc values were not significantly different between the follicular and the luteal phases. In the patients, the values were significantly lower during the luteal phase than during the follicular phase. Lower levels of zinc during the luteal phase in PMS patients, compared with the controls, were noted. Copper levels were noted to be higher during the luteal phase in PMS patients compared with the controls. Because copper competes with zinc for intestinal absorption and serum protein binding sites, zinc:copper ratio can reflect the availability of zinc in the body. The computation of this ratio revealed that the ratio was significantly lower in the patients than those in the controls during the luteal phase.

CONCLUSIONS

Our data suggest that zinc deficiency occurs in PMS patients during the luteal phase, and the availability of zinc in PMS patients during the luteal phase is further reduced by the elevated copper.

Interest of zinc determination in leucocyte fractions for the assessment of marginal zinc status

In order to test the sensitivity of leucocyte zinc determination in the assessment of zinc status, an isolation procedure of mononuclear (MNC) and polymorphonuclear (PMNC) cell fractions was developed. Zinc concentrations in cells from healthy subjects were (mean +/- SD, in mumol/10(10) cells): 0.81 +/- 0.24 in MNC and 0.55 +/- 0.06 in PMNC. In patients suffering from several diseases known to be associated with a marginal impairment in zinc status (cirrhosis, cancer, obesity, endocrine and rheumatic diseases), these concentrations did not differ from those in controls except in rheumatic patients in whom MNC zinc was increased (1.05 +/- 0.42 mumol/10(10) cells) and correlated with erythrocyte sedimentation rate (r = 0.41, P less than 0.01). This relation was also significant in the whole study population (r = 0.39, P less than 0.01). Leucocyte zinc therefore appears to have a limited value in the assessment of marginally impaired zinc status, except in inflammatory states.

Correlation between concentrations of magnesium, zinc, and potassium in plasma, erythrocytes and muscles

In 93 patients, consecutively subjected to laparotomy, we studied the correlation between concentrations of magnesium, zinc and potassium in plasma, erythrocytes and muscle tissue. Sixteen percent had hypomagnesemia, 27% hypozincemia, and 53% hypokalemia. There was no difference with regard to the concentration of magnesium and zinc in erythrocytes or in muscle tissue between patients with low and patients with normal/high plasma concentrations of these minerals. Potassium concentration per liter erythrocytes was slightly but significantly higher in patients with hypokalemia than in patients with normal plasma potassium. When expressed per mmol haemoglobin there was, however, no difference in erythrocyte potassium between these two groups. Neither did they differ with regard to potassium concentration in muscles. There was a highly significant correlation between the concentrations of magnesium, zinc and potassium in erythrocytes as well as in muscle tissue, and a significant correlation between magnesium and potassium in plasma. However, no correlation was found between the mineral concentrations in plasma, erythrocytes and muscles, neither for magnesium, nor for zinc or potassium. We therefore conclude that a valid test to estimate total body stores of these minerals cannot be based on analysis of erythrocytes.

Appraisal of the methodology and applications for measurement of the zinc content of blood components as indicators of zinc status

Methods for the measurement of the zinc content of blood components (plasma, erythrocytes, platelets, mononuclear leukocytes, and polymorphonuclear neutrophils) as indicators of the zinc status of animals have been reviewed and evaluated. The values of plasma or serum zinc concentrations as indicators of zinc status in experimental animals or humans is questionable. Consequently, the zinc content of blood cellular components has been suggested as better indicators of zinc status. Methodological problems, such as incomplete cellular separation or zinc contamination, occur in some of the procedures applied to the quantitation of blood cellular component zinc. Specialized microprobe procedures involving, for example, proton-induced X-ray fluorescence, scanning ion technology, mass spectrometery, or laser microprobe mass analysis might be used to measure the absolute zinc level in individual cells subjected to minimal handling. Then, more conventional methods can be tested against the true standard. Nevertheless, there appears to be species differences in regard to the response of blood cellular zinc concentrations to dietary zinc deficiency. Blood cellular component zinc is conserved during severe zinc deficiency in the rat. In contrast, the zinc content of blood cellular components in humans may reflect the whole body zinc status.