Zinc metabolism in humans after oral and intravenous administration of Zn-69m

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Abstract
Seventeen patients were studied after separate oral and intravenous administration of 50 µCi Zn-69m to determine if Zn-69m is suitable for studying zinc metabolism in humans and to determine if the route of administration affects kinetics. Patients stayed on a metabolic ward for each study. Activity was measured in the total body, urine, feces, blood, plasma, red blood cells, and by detectors over liver and thigh. Five day urine to fecal ratios were 0.44 (intravenous), 0.018 (oral). Most activity went rapidly to liver, then followed two component exponential loss patterns in both cases. Thigh area doubling time was 5.7 days whether the zinc was given orally or intravenously. Plasma activity decreased to less than 2% of that injected by 24 hr after intravenous administration and decreased from a maximum of 1.2% of that ingested, 3 hr after oral administration to 0.7% by 24 hr. Red blood cell activity increased through the 5-day study period to maximum values of 6.4% of that injected after intravenous administration and 2.4% of that ingested after oral administration. Similar metabolic patterns were observed regardless of whether Zn-69m was administered intravenously or orally, suggesting that these patterns were not affected by the mode of administration for the cases studied.