Radioiodine-Labeling of Chlorpyrifos and Its Biodistribution in Mice

To investigate the preparation of radioiodinated Chlorpyrifos and its biodistribution in mice, Chlorpyrifos was labeled with¹³¹I using the Iodogen method. Biodistribution studies were carried out in KM mice. At different times after radiopharmaceutical i.v. administration (185 kBq¹³¹I-Chlorpyrifos/mouse, n=5), the animals were sacrificed. Blood samples and the tissues of interested were collected, weighted and counted. The percentage of injected does per gram (%ID/g) was calculated for each sample. The labeling yield of ¹³¹I-Chlorpyrifos was 93.5%, The radiochemical purity (RCP) was 96.9%. Biodistribution in mice demonstrated that¹³¹I-Chlorpyrifos was extensive, and the uptakes mainly occur in lung, stomach, small-intestine, colon, musle, and submaxillay gland, as indicated by their amount of 37.12%ID/g, 6.18%ID/g, 8.12%ID/g, 8.15%ID/g, 7.04%ID/g, and 7.02%ID/g at 10 min, respectively. And it was metabolized in liver and kidney, as indicated by their uptake of 4.34%ID/g and 8.50%ID/g at 5 min, and 0.22%ID/g and 0.69%ID/g at 4 h, respectively. In addition,¹³¹I-Chlorpyrifos was cleared out from blood quickly, and the uptake of¹³¹I-Chlorpyrifos in blood was 37.27%ID/g at 5 min, and decreased to 1.35%ID/g at 4 h post injection. In conclusion, ¹³¹I-Chlorpyrifos was stable in vitro and it was absorbed in lung and digestive tract, and it was metabolized mainly in liver and kidney, worthy of further investigation to trace the compound in vivo and in vitro.