Membrane potential determination in large unilamellar vesicles with hexakis(2-methoxyisobutylisonitrile)technetium(I).
The accumulation of the lipophilic cation hexakis (2-methoxyisobutylisonitrile)technetium (99mTc-MIBI) within large unilamellar vesicles made from egg phosphatidylcholine was examined as a function of time and membrane potential (Em). Equilibrium distribution occurred within minutes at 30 degrees C. The transmembrane distribution of Tc-MIBI was measured at Em = 0 mV and at a series of negative membrane potentials. The distribution of Tc-MIBI was in close agreement with the Nernst equation for passive distribution of a permeant ion across a bilayer, permitting the membrane potential to be predicted from Tc-MIBI distribution. In this respect, Tc-MIBI behaves similarly to other radioprobes of membrane potential, but with unique properties including high specific activity (10(9) Ci/mol), rapid kinetics of distribution, low potential-independent binding, and short half-life (6.02 h). The results indicate a mechanism for tissue accumulation of Tc-MIBI in vivo that may in part account for its utility in clinical imaging of ischemic myocardium.
Chernoff
D M
DM
Department of Radiology, Harvard Medical School, Boston, MA.
Strichartz
G R
GR
Piwnica-Worms
D
D
D008564:Membrane Potentials; D008566:Membranes; D008567:Membranes, Artificial; D017202:Myocardial Ischemia / Q000378:metabolism; D010713:Phosphatidylcholines; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics
D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D017256:Technetium Tc 99m Sestamibi