Fig. 1

Schematic representation of the proposed cellular mechanism that explains localization of ^99mTc-sestamibi in renal oncocytomas and HOCTs. ^99mTc-sestamibi diffuses across cell membranes and is able to accumulate in cells with large numbers of functioning mitochondria on the basis of an affinity for the high negative mitochondrial membrane potential. This intracellular accumulation does not occur in cells with few or non-functional mitochondria and can be overcome by the activity of MDR pumps that actively excrete small organic molecules such as ^99mTc-sestamibi