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Comparison of Scandium-46 and Cerium-144 as Nonabsorbed Reference Materials in Studies with Cattle¹

Agricultural Research Laboratory of The University of Tennessee, Oak Ridge, Tennessee 37830²

The suitability of ⁴⁶Sc as a nonabsorbed reference material for cattle was investigated by simultaneous within-animal comparison with ¹⁴⁴Ce which has previously been used for this purpose. Excretions and tissue distributions of ⁴⁶Sc and ¹⁴⁴Ce were compared in six calves and twelve mature cattle. Tracer levels of both nuclides were given to two calves intravenously, to two as single oral doses, and to two as daily oral doses. Older animals were given either ⁴⁶Sc or ¹⁴⁴Ce as daily oral doses. Blood ⁴⁶Sc and ¹⁴⁴Ce, expressed as percentages of concentrations found 5 minutes after intravenous administration, decreased respectively from 88 and 30% at 15 minutes to 33 and 0.9% at 10 hours. Urinary ⁴⁶Sc and ¹⁴⁴Ce averaged 0.1 and 0.2% of intravenous doses. Neither radioisotope was detected in blood or urine after oral dosage, and recovery in feces was almost complete. Similar gastrointestinal distributions of the two nuclides were found at slaughter, and adsorption to undigested residues averaged 92% for ⁴⁶Sc and 95% for ¹⁴⁴Ce. Tissues accounting for totals of 40 and 36% of intravenous ⁴⁶Sc and ¹⁴⁴Ce doses contained barely detectable traces of oral doses. These results indicate ⁴⁶Sc is as suitable as ¹⁴⁴Ce for use as a nonabsorbed reference material for cattle. Scandium-46 could substitute in mixtures with certain other radioisotopes where ¹⁴⁴Ce would be unsuitable because of its counting characteristics.

² Operated by the Tennessee Agricultural Experiment Station for the U. S. Atomic Energy Commission under Contract No. AT-40-1-GEN-242.

Manuscript received 22 May 1970.