Distribution of label after intragastric administration of 7Be-labeled carbon to weanling and aged mice.

Single doses of 7Be-labeled carbon particles prepared by proton bombardment of carbon black were administered by gavage to weanling (4 weeks) and aged (18 months) mice. Body distribution of 7Be radioactivity was determined 4 hr and 1, 2, 5, and 14 days later. The results were compared with those obtained after administration of a solution of 7BeCl2. 7Be radioactivity in nonintestinal tissues was 17-58 times greater in mice gavaged with the soluble salt than in those gavaged with the particles, indicating that particle-bound 7Be was well confined to the gastrointestinal tract. Upper limits of the amount of labeled carbon remaining in intestinal Peyer's patches were as follows: 1 day: weanling, 1.8 X 10(-3)%, old, 5.5 X 10(-3)%; 15 days: weanling, 3.3 X 10(-5)%, old, 8.4 X 10(-5)%. The particles are potentially useful as models for diesel emissions or other particulate pollutants.