In vitro radioautographic studies of the biodistribution of radiopharmaceuticals on blood elements.

In the present study we evaluated the binding of the radiopharmaceuticals sodium pertechnetate (Na 99mTcO4), methylenediphosphonic acid (99mTc-MDP) and glucoheptonate acid (99mTc-GHA) to blood elements using centrifugation and radioautographic techniques. Heparinized blood was incubated with the labelled compounds for 0, 1, 2, 3, 4, 6 and 24 h. Plasma (P) and blood cells (BC) were isolated and precipitated with 5% trichloroacetic acid (TCA), and soluble (SF) and insoluble fractions (IF) were separated. Blood samples were prepared (0 and 24 h) and coated with LM-1 radioautographic emulsions and percent radioactivity (%rad) in P and BC was determined. The binding of Na 99mTcO4 (%rad) to P was 61.2% (0 h) and 46.0% (24 h), and radioautography showed 63.7% (0 h) and 43.3% (24 h). The binding to BC was 38.8% (0 h) and 54.0% (24 h), and radioautography showed 36.3% (0 h) and 56.7% (24 h). 99mTc-MDP study presented 91.1% (0 h) to P and 87.2% (24 h), and radioautography showed 67.9% (0 h) and 67.4% (24 h). The binding to BC was 8.9% (0 h) and 12.8% (24 h), and radioautography showed 32.1% (0 h) and 32.6% (24 h). 99mTc-GHA study was 90.1% (0 h) to P and 79.9% (24 h), and radioautography showed 67.2% (0 h) and 60.1% (24 h). The binding to BC was 9.9% (0 h) and 20.1% (24 h), and radioautography showed 32.8% (0 h) and 39.9% (24 h). The comparison of the obtained results suggests that the binding to plasma and blood cells in the two techniques used (radioautography and centrifugation) is qualitatively in accordance.

In vitro effect of cyclophosphamide on the binding of radiopharmaceuticals (99mTcO4- and 99mTc-MDP) to blood elements.

Sodium pertechnetate (99mTcO4-) and many 99mTc-products are the radiopharmaceuticals most frequently used in nuclear medicine. Using an in vitro model, we evaluated the effect of cyclophosphamide on percent radioactivity of 99mTcO4- and methylenediphosphonic acid (99mTc-MDP) bound to isolated blood elements. Blood samples were incubated with the two radiopharmaceuticals, plasma and blood cells were separated and precipitated, and soluble and insoluble fractions were separated. To evaluate the effect of cyclophosphamide, blood was incubated with this drug 1 h prior to the addition of the radiopharmaceuticals. The fraction of 99mTcO4- radioactivity was slightly higher in plasma (61.2 to 53.8%) than in blood cells (38.8 to 46.2%) up to 6 h and cyclophosphamide did not interfere with this distribution. The amount of 99mTc-MDP radioactivity was higher in plasma (91.1 to 87.2%) than in blood cells (8.9 to 12.8%) up to 24 h and cyclophosphamide did not modify it. The binding of 99mTcO4- to the insoluble fraction of plasma (4.9 to 6.1%) was low and cyclophosphamide did not interfere with it up to 6 h, but a small blockade (9.8 to 4.8%) was observed at 24 h. From 3 h on, cyclophosphamide slightly inhibited 99mTcO4- binding to blood cells (23.1 to 16.6%) and increased it at 24 h (31.2 to 14.3%). Cyclophosphamide did not alter 99mTc-MDP binding to the insoluble fraction of blood cells and slightly decreased 99mTc-MDP binding to the insoluble fraction of plasma (29.8 to 23.6%) up to 6 h.(ABSTRACT TRUNCATED AT 250 WORDS)