Absorption, Excretion, and Tissue Distribution of Orally and Intravenously Administered Radiocerium as Affected by EDTA

Abstract

Three pairs of calves fed 0, 1.35, or 13.5g ethylenediaminetetraacetic acid (EDTA) per calf by capsule daily and one pair fed 13.5g EDTA in milk through nipple pails were given intravenous 141Ce and oral 144Ce as simultaneous single doses. Oral 144Ce could not be detected in blood and intravenous 141Ce cleared rapidly with less than 16 and 0.6% remaining in blood 1 and 24 hours after dosing. Urinary 144Ce increased from 0.01% of the oral dose for controls to 0.21% when 1.35g EDTA was fed. Percentages of the 144Ce dose in urine were further increased to 0.56 for calves fed 13.5g EDTA by capsule and 1.21% for calves fed 13.5g by nipple pail. Urinary 141Ce was raised slightly from 1.2% of the intravenous dose for controls to 1.6 by 1.35g EDTA, to 5.27% by 13.5g in gelatin capsules, and to 9.75% by 13.5g given through nipple pails. Entry of intravenous 141Ce into the digestive tract occurred primarily in the small intestine. Fecal excretions and tissue distributions of both oral and intravenous doses were not statistically significantly changed by EDTA. Average 72-hour fecal excretions totaled 94 and 2% for oral and intravenous doses. Tissue 141Ce, expressed as percentages of the intravenous dose per 100g, averaged: heart, 0.04; femur, 0.41; kidney, 0.23; liver, 2.60; lung, 0.75; rib, 0.13; and spleen, 0.67. Oral 144Ce was not detected in any tissue except the liver, which averaged 0.7% of the oral dose compared to 36.7% of the intravenous dose.