UPTAKE, EXCRETION, AND RADIATION HAZARDS OF TRITIATED-THYMIDINE IN HUMANS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 37  (2) , 610-618
Abstract
Nine patients with malignant disease were given i.v. injections of 3H-thymidine, 0.2 mCi/kg, for tumor cell kinetics studies. Serial plasma, urine, saliva and air vapor samples were collected variously for up to 79 days, and 3H activity was measured. The initial half-life of plasma activity was rapid. After 1 day, the activity decayed with a half-life of 10.8 days, indicating equilibration of activity with the total body water. Urine activity was over 100 times the plasma activity within 1 h, with equilibration approaching the plasma activity after 2 days, and then decayed at a similar rate. Saliva and air vapor activity increased to plasma levels and then decayed at the same rate as plasma activity. In the first 24 h, .apprx. 1/3 of the total injected activity was excreted in the urine. During the first 12 days there were 54.2% urinary and 10.6% insensible losses. Maximum losses determined by extrapolation of observed data were 68% urinary and 19.5% insensible losses, or a total of 87.5%. Approximately 7% of the injected activity may represent material initially incorporated into DNA but later metabolized and excreted. The radiation dose from total body water is estimated at 0.69 rad. The estimated dose absorbed by cell nuclei from incorporated material is a maximum of 20.5 rads. These radiation doses would not seem to contraindicate injection of 0.2 mCi 3H-thymidine/kg to patients in this clinical and experimental setting. Measurements of activity in personnel and room air indicate that the use of such doses is not hazardous if appropriate precautions are followed.

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