The preparation of 125I-RC-160 and its in vitro binding characteristics to the receptors of NCI-H446 cell line

To investigate the preparation of 125I-somatostatin analogy (RC-160) and its binding characteristics to NCI-H446 cell receptors. RC-160 was labelled with Na125I using chloramines-T method, then purified by C18 reverse phase chromatography and examined by silica chromatographic paper. Time-binding correlation test, temperature-binding correlation test, saturable binding test and competition binding test between NCI-H446 cells and 125I-RC-160 were carried out. The labelling rate of 125I-RC-160 was 54.34%. The specific activity of 125I-RC-160 was 1.85 TBq/mmol·L-1. The radiochemical purity was 92%. The value of Kd and Bmax was 1.71 x 10-10 mol/L and 1.06 x 105 site/cell respectively. The labelled 125I-RC-160 could be used for receptor analysis and the iodination of RC-160 does not change its binding to somatostatin receptor. The results demonstrated that the binding of 125I-RC-160 to NCI-H446 cell possessed the reversibility, specificity, saturability, and was time and temperature dependent. The NCI-H446 cell line expresses somatostatin receptors with high density and affinity. The binding is in accordance with single site system