Objectives: To investigate DNA double-strand breaks (DSBs) in blood lymphocytes induced by two-day 99mTc-MIBI myocardial perfusion scintigraphy (MPS) using y-H2AX immunofluorescence microscopy and to correlate the results with 99mTc activity in blood samples.
Methods: Eleven patients who underwent two-day MPS were included. DSB blood sampling was performed before and 5min, 1h and 24h after the first and second radiotracer injections. 99mTc activity was measured in each blood sample. For immunofluorescence microscopy, distinct foci representing DSBs were quantified in lymphocytes after staining for the phosphorylated histone variant y-H2AX.
Results: The 99mTc-MIBI activity measured on days one and two was similar (254±25 and 258±27 MBq; p=0.594). Compared with baseline DSB foci (0.09±0.05/cell), a significant increase was found at 5min (0.19±0.04/cell) and 1h (0.18±0.04/cell) after the first injection and at 5min and 1h after the second injection (0.21±0.03 and 0.19±0.04/cell, respectively; p=0.003 for both). At 24h after the first and second injections, the number of DSB foci had returned to baseline (0.06±0.02 and 0.12±0.05/cell, respectively). 99mTc activity levels in peripheral blood samples correlated well with DSB counts (r=0.451).
Conclusions: DSB counts reflect 99mTc-MIBI activity after injection for two-day MPS, and might allow individual monitoring of biological effects of cardiac nuclear imaging.
Key points: • Myocardial perfusion scintigraphy using 99mTc induces time-dependent double-strand breaks (DSBs) • γ-H2AX immunofluorescence microscopy shows DSB as an early response to radiotracer injection • Activity measurements of 99mTc correlate well with detected DSB • DSB foci induced by 99mTc return to baseline 24h after radiotracer injection.
Keywords: Coronary artery disease; DNA double-strand breaks; Gamma-H2AX; Myocardial perfusion scintigraphy; Tc-MIBI.