Interaction of technetium 99m-labeled teboroxime with red blood cells reduces the compound’s extraction and increases apparent cardiac washout
99mTc-labeled teboroxime shows high myocardial extraction in both in vivo animal and in vitro cell culture and isolated heart studies. Whereas in vivo studies show rapid myocardial clearance of teboroxime, in vitro cell culture and isolated heart studies show slower washout comparable to that of201Tl. Binding of teboroxime to blood components may contribute to these conflicting results.
Methods and Results
We measured teboroxime extraction in the isolated blood-perfused rabbit heart after injection in saline solution, brief incubation in red blood cell perfusate, or 4-hour incubation with human red blood cells. Teboroxime in saline solution showed high extraction (Emax=0.89±0.02; Enet=0.69±0.02), whereas brief incubation in perfusate (Emax=0.60±0.06; Enet=0.48±0.05) or prolonged incubation with human red blood cells (Emax=0.43±0.09; Ene=0.38±0.07) resulted in reduced extraction. Teboroxime clearance was similar for all groups and was slower than201Tl clearance. Analysis of total residual cardiac teboroxime (comparable to external imaging) showed that teboroxime clearance was biexponential. Reduced extraction of teboroxime in red blood cells resulted in an increased size of the rapidly clearing (unextracted) fraction, giving the appearance of rapid myocardial washout.
Teboroxime has a high myocardial extraction. Binding to blood components reduces teboroxime extraction and increases the rate of cardiac teboroxime clearance.
Key Wordsteboroxime thallium technetium 99m rabbit isolated heart
Unable to display preview. Download preview PDF.
- 1.Kronauge JF, Chiu ML, Cone JS, et al. Comparison of neutral and cationic myocardial perfusion agents: characteristics of accumulation in cultured cells. Nucl Med Biol 1992;19:141–8.Google Scholar
- 10.Deutsch E, Ketring AR, Libson K, Vanderheyden J-L, Hirth WW. The Noah’s ark experiment: species dependent biodistributions of cationic99mTc complexes. Nucl Med Biol 1989;16:191–232.Google Scholar
- 12.Dahlberg ST, Gilmore MP, Siwko R, Leppo JA. Incubation with red blood cells reduces the extraction of technetium-99m teboroxime in the isolated rabbit heart [Abstract]. J Nucl Med 1991;32:910.Google Scholar
- 18.Bassingthwaighte JB, Raymond GM, Chan JI. Principles of tracer kinetics. In: Zaret BL, Beller GA, eds. Nuclear cardiology: state of the art and future directions. St Louis: Mosby-Year Book, 1993:3–23.Google Scholar
- 20.Bassingthwaighte JB, Goresky CA. Modeling in the analysis of solute and water exchange in the microvasculature. In: Renkin EM, Michel CC, eds. Handbook of physiology: the cardiovascular system, vol 4: the microcirculation. Bethesda, Maryland: American Physiological Society, 1984:549–626.Google Scholar
- 27.Stone JA, Dawood F, Wen W-H, McLaughlin PR, Liu PP. Is the myocardial uptake of teboroxime viability dependent? [Abstract]. Circulation 1992;86:I-707.Google Scholar
- 28.Beanlands RS, Palser A, Hartman N, Aung M, Ruddy TD. Are the kinetics of Tc-99m-teboroxime altered in the postischemic myocardium? (Abstract). Circulation 1993;88:249.Google Scholar