Rapid enzymatic pretreatment of samples before determining chromium in serum or plasma.

A simplified method for preparing blood serum and plasma for Zeeman electrothermal atomic absorption spectrometry is described and applied to the measurement of chromium in human serum and plasma. This enzymatic degradation with bacterial protease (EC 3.4.21.3) requires little laboratory apparatus, decreases the work and time of sample preparation, and obviates some potential sources of contamination. We used bovine reference serum (USDA No. 7292) to validate Cr concentration. There was less Cr in serum than in plasma, whether sodium heparin or sodium citrate was used as anticoagulant. For six human subjects, Cr in serum averaged 0.15 (SD 0.02) micrograms/L, 0.26 (SD 0.03) micrograms/L in heparinized plasma, and 0.28 (SD 0.02) micrograms/L in citrated plasma. We postulate that the Cr concentration is lower in serum because some of the Cr binds to proteins complexed with the clot in the coagulation process.

The effects of inorganic chromium and brewer's yeast on glucose tolerance, plasma lipids, and plasma chromium in elderly subjects.

Twenty-three healthy, well-nourished, free-living elderly volunteers were given daily, for 10 wk, 5 g brewer's yeast, 200 micrograms Cr3+ as chromic chloride (CrCl3), or placebo. There were no significant changes in glucose tolerance, insulin, cholesterol or triglycerides after supplementation in any of the three groups. Plasma Cr3+ rose significantly after supplementation with CrCl3 but did not change after yeast or placebo supplementation. Plasma Cr3+ did not increase after an oral glucose load and did not correlate with glucose, insulin or lipid values in any of the groups. Calculated intakes of eight indicator nutrients were well above 100% of the RDA except for calcium. These healthy elderly persons, eating nutritious diets, are not at risk for Cr3+ deficiency as measured by the absence of a clinical response to CrCl3 or brewer's yeast supplementation. This study suggests that age per se is not a factor leading to Cr deficiency.