Radium (Ra 226 ) and Radon (Em 222 ) Metabolism in Dogs

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Abstract
The fractional Ra226 content of beagle dogs decreases after intravenous injection according to the function 0.787 t-0.198, where t is in days. About 80% of the radon is exhaled during the first few years after injection. Since radon exhaltion is approximately equal in other species, a theoretical approach based on radon recoil ranges and bone ultra-structure is suggested to account for this fact. Retention of Ra226 and Ca45 in dogs is essentially equal (to 100 days after injection), due to cancellation of differences in three factors (renal clearance rate, plasma level, and skeletal binding). Ra226 metabolism is dependent on age; retention decreases with age at injection, the reverse is true for plasma levels. Beagles injected with the smaller amounts of Ra226 correspond to humans containing 0.1-1.0 [mu]c. Since this is a range of extreme importance in setting maximum permissible levels, these dogs are being carefully observed for the appearance of radiation effects; some rontgenographic changes have already been seen.