Zinc Metabolism in Patients on Maintenance Hemodialysis

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Abstract
Recent studies have focused attention on the possible role of zinc depletion in the pathogenesis of uremic symptoms such as dysgeusia and impotence. The present studies were undertaken to evaluate the prevalence of zinc deficiency and abnormalities of zinc metabolism in patients with end-stage renal disease. A total of 43 stable chronic hemodialysis patients were screened for evidence of zinc deficiency by measurement of fasting predialysis leukocyte and plasma zinc. The results were compared with those from 30 healthy volunteers. Seventeen of these 43 patients had 65Zn absorption measured, and in 9 the rate of disappearance of 65Zn from the body was also measured. The results were compared with those obtained in 20 healthy controls. The nutritional status of these 17 patients was estimated by global nutritional assessment and calculation of the Quetelet index while 9 of 17 had dietary zinc intake calculated from a diet history. The mean plasma zinc level was lower in the hemodialysis patients (11.7 .+-. 2.3 .mu.mol/l vs. 13.3 .+-. 2.9 .mu.mol/l in controls; p < 0.05). The mean leukocyte zinc level was 0.81 .+-. 0.27 .mu.mol/g dry weight in dialysis patients and 0.81 .+-. 0.22 .mu.mol/g in controls (p > 0.2). The mean 65Zn absorption in the patients was 49 .+-. 14% and in controls 53 .+-. 12% (p > 0.2). Mean turnover of body 65Zn was 0.47 .+-. 0.11%/day in patients and 0.43 .+-. 0.18% day in controls (p > 0.1). The mean 65Zn half-life was 154 .+-. 29 days in patients and 187 .+-. 75 days in controls (p > 0.05). Nine patients were regarded as undernourished. The mean leukocyte zinc level in these patients was 0.53 .+-. 0.21 .mu.mol/g and 0.64 .+-. 0.29 .mu.mol/g in the 8 well-nourished patients (p < 0.05). The mean 65Zn absorption in the undernourished patients was 44 .+-. 18% and 53 .+-. 10% in the well-nourished patients (p > 0.1). Dietary zinc was normal (10.2 .+-. 4.8 mg/day) and did not correlate with plasma zinc, leukocyte zinc, or 65Zn absorption. Conclusions: (1) 65Zn absorption and retention are normal in stable chronic hemodialysis patients; (2) though undernourished dialysis patients are zinc depleted as evidenced by low leukocyte zinc. 65Zn absorption is normal, suggesting that zinc malabsorption is not the cause of zinc depletion, and (3) because significant zinc malabsorption was not evident in our patients nor impairment of body 65Zn turnover or half-life, the lowered leukocyte zinc levels observed in undernourished subjects may reflect alterations in body distribution of zinc rather than lowered zinc status.