Effects of ion channel modulators in the influx and efflux of Tc-99m-MIBI

Abstract

Possible involvement of cell membrane ion transport systems in the uptake and extrusion of Tc-99m-MIBI was investigated by using various buffers with or without Na+ and Ca++, and ion transport inhibitors in a tumor cell line. The ion transport modulators dimethyl amiloride (DMA), verapamil, flunarizine and monensin were used. The uptake of Tc-99m-MIBI was significantly increased in all buffers containing either Na+ or Ca++ alone or none of them. There was significantly increased uptake of Tc-99m-MIBI especially in buffers without Na+. Verapamil, a L-type Ca++ channel blocker, increased Tc-99m-MIBI uptake in all buffers. Flunarizine, which inhibits Na+/ Ca++ channels, caused significantly increased accumulation of Tc-99m-MIBI only in buffer containing both Na+ and Ca++. Monensin, a sodium ionophore, significantly increased uptake of Tc-99m-MIBI. DMA, a potent Na+/H+ antiport inhibitor, significantly inhibited the uptake of Tc-99m-MIBI in all buffers. In conclusion, Tc-99m-MIBI behaves like Na+ during its uptake and extrusion. Extrusion of Tc-99m-MIBI may involve both verapamil- and flunarizine-sensitive pathways.

Role of thyroid scintigraphy vs. fine needle aspiration cytology in the clinical evaluation of solitary thyroid nodule a clinicoradiopathologic study

“…On the other hand, the current study revealed high uptake (C) in high grade malignancy with lower degree of uptake in low grade malignancy which is attributed to the dense mitochondrial activity in higher Na + /Ca ++ exchange channels in the cell membrane as stated by Arab et al (1998 and 1999) [15,16] . This is why the current study revealed low sensitivity to detect malignancy and in addition the use of the suitable cut-off of retention index mean + 1.5 SD (14%).…”

Technetium-99m-Tetrofosmin Would Be a Substrate for Multidrug Resistance-associated Protein (MRP): Comparison between a Leukemia Cell Line with High MRP Gene Expression and Its Parental Cell Line

“…Previous reports showed that verapamil increased the 99m Tc-MIBI accumulation in several tumor cell lines without detectable P-gp expression. 5,15,18 Although it is possible that small amounts of MRP or P-gp was not detected by the techniques used in this study, these findings rather indicated that verapamil would affect the tracer uptake partly through a mechanism other than the inhibition of P-gp or MRP function. Verapamil, as a calcium antagonist and K 1 channel blocker, 19 decreases the intracellular Ca 11 and K 1 concentration, and then secondarily increases intracellular Na 1 concentration.…”

Lower limb perfusion scintigraphy with 99mTc-MIBI scintigraphy and determination of endothelin in diabetic and nondiabetic patients

“…Perfusion scintigraphy using technetium-99m -methoxyisobutyl isonitrile ( 99m Tc-MIBI) can be very useful for evaluation of the lower limbs muscle perfusion. After intravenous application, 99m Tc-MIBI is rapidly cleared from the circulation and preferentially is accumulated in muscular tissues (including heart) proportionally to regional blood flow 6,7 . These characteristics of 99m Tc-MIBI make it very suitable for examining regional blood flow, visualization with gamma camera, as well as getting quantita-tive parameters for regional blood flow changes, including quantitative assessment of tissue perfusion in basal conditions (rest study) and after workload (stress study).…”