Circadian variation in copper and zinc in man.

LIFSCHITZ, M. D., AND R. I. HENKIN. Circadian variation in copper and zinc in man. J. Appl. Physiol. 31(l): 88-92. 1971.~Copper and zinc metabolism were studied in 10 normal volunteers on a constant regimen consisting of an alternate 4 hourly intake of a liquid diet or distilled water, and a regulated amount of activity. Urine was collected in 4-hr periods and blood samples drawn in the middle of these periods. A circadian pattern of variation for serum copper and zinc concentration was demonstrated; serum copper was above the mean at 10 : 00 AM and 2 : 00 PM, at the mean at 6 :00 PM and 10 :00 PM, and below the mean at 2 :00 AM and 6 :00 AM. Serum zinc was above the mean from 10 :00 AM to 10 :00 PM and below the mean at 2 : 00 AM and 6 :00 AM. This pattern persisted in two subjects who received 2.5 mg of prednisolone every 6 hr for 3 days. A circadian pattern for the urinary excretion of copper but not for zinc was demonstrated. Serum ceruloplasmin tended to follow serum copper concentrations, and suggested that the regulation of metal binding proteins may be important in the circadian pattern of these metals observed in serum.