OBJECTIVE(99)Tc(m) labeled C2A domain of synaptotagmin I ((99)Tc(m)-Syt I-C2A) is used for noninvasive detection of vulnerable atherosclerotic plaque.

METHODSRecombinant C2A domain of synaptotagmin I, overexpressed in E. Coli, was thiolated with 2-iminothiolane (2-IT) and labeled with (99)Tc(m). Atherosclerotic plaques were produced in 5 rabbits by deendothelialization of the abdominal aorta and the rabbits were fed with cholesterol diet for 3 months. Three rabbits not manipulated served as normal controls. All animals were injected with (99)Tc(m)-Syt I-C2A and underwent in vivo imaging thereafter. Aortas were then explanted for ex vivo imaging and histological characterization.

RESULTSIn deendothelialized animals, intense radio-uptake in abdominal aorta, showed by gamma camera at 2 h after injection, was visualized and T/B was 3.25 +/- 0.51 by ROI measurement, quantitative uptake ratio of abdominal aortas with atherosclerotic lesions to thoracic aortas was 8.39 +/- 1.74 in ex vivo imaging. The mean uptake in specimens of abdominal aortas with lesions was 12.6-fold higher than in control abdominal aortas, and 10.2-fold higher than in thoracic aortas of deendothelialized animals by gamma-counter.

CONCLUSION(99)Tc(m)-Syt I-C2A has a high affinity for vulnerable atherosclerotic plaque and is a suitable a gent for the noninvasive detection of vulnerable atherosclerotic plaque.