Visualization of Dynamic Expression of Myocardial Sigma-1 Receptor After Myocardial Ischemia and Reperfusion Using Radioiodine-Labeled 2-[4-(2-iodophenyl)piperidino]cyclopentanol (OI5V) Imaging

Background: This study chronologically evaluated the expression of the intensity and distribution of the sigma-1 receptor (σ1R) demonstrated by radiolabeled 2-[4-(2-iodophenyl)piperidino]cyclopentanol (OI5V) in a rat model of myocardial ischemia and reperfusion.

Methods and results: The left coronary artery was occluded for 30 min, followed by reperfusion. Dual-tracer autoradiography with ¹²⁵I-OI5V and ^{99 m}Tc-MIBI was performed to assess the spatiotemporal changes in ¹²⁵I-OI5V uptake (n=5-6). Significant and peaked ¹²⁵I-OI5V uptake in the ischemic area was observed at 3 days after reperfusion, and the ¹²⁵I-OI5V uptake ratio of ischemic area to normally perfused left ventricular area decreased gradually from 3 to 28 days (mean value±SD; 0.90±0.12 at 1 day, 1.89±0.19 at 3 days, 1.52±0.17 at 7 days, 1.34±0.13 at 14 days, and 1.16±0.14 at 28 days, respectively). Triple-tracer autoradiography with ¹²⁵I-OI5V, ^{99 m}Tc-MIBI, and ²⁰¹TlCl was performed to evaluate ¹²⁵I-OI5V uptake in the ischemic area in relation to the residual perfusion at 7 days (n=4). The ¹²⁵I-OI5V uptake ratio of the non-salvaged area was higher compared to that of the salvaged area in the ischemic area. ¹²³I-OI5V and ^{99 m}Tc-MIBI SPECT/CT was performed 3 days after reperfusion (n=3), and the in vivo images showed clear uptake of ¹²³I-OI5V in the perfusion defect area.

Conclusions: The present study confirmed the spatiotemporal expression pattern of σ1R expression. Non-invasive σ1R imaging with ¹²³I or ¹²⁵I-OI5V was feasible to monitor the expression of σ1R after myocardial ischemia and reperfusion.