\s=b\The plasma zinc concentration and quantitative urinary zinc excretion were studied in 105 pediatric patients with the nephrotic syndrome or nephritis-nephrosis. The plasma level was decreased to a mean value of 51.7 \g=m\g/dLin patients with the nephrotic syndrome (controls, 85 \ g=m\ g/ dL). The rate of urinary zinc excretion was not different from that of the controls, with the exception of patients whose disease was in the polyuric phase of beginning remission where it was fivefold higher and those who had achieved a long-lasting remission of the disease. Since about two thirds of the plasma zinc is bound to albumin, an unchanged zinc-albumin ratio would reflect an equal zinc and albumin loss. The ratio, however, was increased twofold and thus does not adequately explain the hypozincemia. The low hair level of 86 \g=m\g/g may suggest a more profoundly disturbed zinc metabolism than originally thought.(Am J Dis Child 134: [46][47][48][49][50] 1980) Our interest in studying the plasma concentration and excretory rate of zinc in patients with nephrotic syndrome was stimulated by two observations. In 1942, McCance and Widdowson1 described two patients with albuminuria that was accompa¬ nied by a substantially increased zinc excretory rate. In contrast, Fairhall and HoyU had found earlier an essen¬ tially unchanged rate of zinc excretion in nephritis or nephrosis. In 1972, when studying the aminonucleoside nephrosis of rats, Freeman et al·1 observed an increase in the rate of zinc excretion almost parallel to the increase in the rate of protein excre¬ tion. At the same time, the plasma zinc levels decreased below normal. The second observation refers to stud¬ ies of Flynn et al· who reported a precipitous decrease in serum zinc concentration during corticosteroid treatment and who suspected a rela¬ tion to the adrenocorticotropic hor¬ mone production or corticosteroid se¬ cretion.We decided, therefore, to study changes in the metabolism of zinc in patients with the nephrotic syndrome, a disease that by definition is accom¬ panied by substantial proteinuria. In addition, most pediatrie patients with the nephrotic syndrome receive pro¬ longed corticosteroid treatment. Our results show that the plasma zinc level is decreased in patients with the ne¬ phrotic syndrome as long as proteinu¬ ria is present. The rate of urinary zinc excretion, however, is not increased and shows little change during the course of the nephrotic syndrome. SUBJECTS AND METHODSA total of 105 pediatrie patients who fulfilled the criteria for the nephrotic syndrome (anasarca, proteinuria, hypoalbuminuria, hypercholesterolemia), or glomerulonephritis and nephrotic syndrome (proteinuria, persistent hematuria, tran¬ sient or constant mild hypertension) were included in this study. They were sepa¬ rated into two groups, 81 patients with idiopathic nephrotic syndrome and 24 patients with a combination of nephritisnephrosis. Studies were also performed in seven patients with glomerulonephritis, but because of the small number, the data were no...

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We undertook detailed examination of the practices and procedures involved in the analysis of serum for zinc by atomic absorption spectrophotometry, to identify possible sources of zinc contamination. Some degree of contamination was found in almost all steps of the procedure. These findings are presented and alternative materials and procedures are described that significantly decrease or eliminate contamination from extraneous zinc. The plasma of 76 normal adults was analyzed by the revised procedure, and a lower mean value was obtained than has been previously reported.

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