STRONTIUM85 AND CALCIUM45 METABOLISM IN MAN 12

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Abstract
The metabolism of intravenously and orally administered radiostrontium and radiocalcium was studied in man. Sr85 a gamma-emitter with a 65 day half life and Ca45 were used as tracers. The main pathway of excretion is via the kidney irrespective of the route of entry of the isotope. The urinary Sr85 excretion varied from patient to patient and depended on the state of Ca metabolism; it was lowest in a patient with Paget''s disease of the bone. Following the oral administration of the Sr tracer an average of 80% of the administered dose passed unabsorbed with the stool. A method is described to determine the endogenous fecal Sr excretion in man and values for four patients are listed. The endogenous fecal Sr excretion is approximately 10% of the absorbed dose. The metabolism of radiostrontium following the intravenous and oral routes was compared in 4 patients and good agreement was noted. The metabolism of radiocalcium and of radiostrontium was compared in the same subjects: Sr is absorbed poorer from the intestinal tract and is better excreted via the kidney than Ca. Therefore, the body burden of Sr is considerably less than that of Ca.