Factors underlying abnormal zinc metabolism in uremia

Zinc balance studies were completed in ten hemodialyzed adult uremic patients and five normal controls to determine the cause of abnormal zinc metabolism in uremia. Subjects were fed standard hospital foods providing nutrients in amounts recommended for adult stable hemodialyzed patients. The amount of zinc in the diet was kept constant at 10 mg per day. After one week of stabilization, blood, urine, used dialysate (in patients on dialysis days) and stool samples were collected daily for the next two weeks. In comparison to controls, patients had lower plasma zinc levels (mean +/- SD, 112 +/- 10 vs. 82 +/- 12 micrograms/dl, P less than 0.01), lower urinary zinc excretion (560 +/- 120 vs. 40 +/- 20 mg/24 hrs, P less than 0.001) and higher fecal zinc losses (8.1 +/- 0.7 vs. 10.2 +/- 0.6 mg/24 hrs, P less than 0.01). Dialytic zinc losses were minimal (26 +/- 4 micrograms/treatment). During the study period, patients were in a negative zinc balance while normal controls maintained a positive zinc balance on 10 mg dietary zinc intake. These results demonstrate that augmented fecal zinc excretion in the presence of hypozincemia contributes to the negative zinc balance in hemodialyzed uremic patients.