Divergent Kinetics of 201T1 and 99mTc-SESTAI4IBI in Cultured Chick Ventricular Myocytes During ATP Depletion

Background. Thallous chloride (2`TI) and hexakis(2-methoxyisobutyl isonitrile) technetium (I) ("'ETcSESTAMIBI) are myocardial perfusion imaging agents with biological properties that also reflect tissue viability. Initial myocellular uptake rates of 201T1 reflect activity of Na,K-ATPase, whereas those of ""'Tc-SESTAMIBI reflect mean plasma membrane potential. Methods and Resul. To better understand the mechanistic responses of these tracers to myocellular injury, cultured chick embryo cardiac myocytes were metabolically inhibited in iodoacetate (1 mM) and rotenone (10 ,uM) for up to 2 hours, and initial uptake rates ofeach agent were determined at successive intervals alongwith correlative cellular contents ofATP, sodium, and potassium and lactate dehydrogenase release. ATP content fell from 30.5±1.4 to 2.7±0.9 nmol * (mg protein)f` within 2 minutes, whereas sodium and potassium contents