Elevated concentrations of mitochondrial peripheral benzodiazepine receptors in ovarian tumors

Using PK 11195, a high affinity ligand for peripheral benzodiazepine receptor (PBZr) binding sites in isolated mitochondria (m-fraction) and microsomal fraction (p-fraction) from human ovaries and ovarian tumors were studied. Binding in both m and p-fractions from ovaries and tumors were saturable and of high affinity. The PBZr density in m- and p-fractions from ovaries was very similar whereas the binding in m-fraction in ovarian tumors was nearly 3-fold higher than p-fraction. There was no significant difference in the binding affinities (KD values) for PK 11195 in the various fractions. The selective increase in the density of PBZr in mitochondria of tumors suggests an association with energy demand and utilization. The role of a relatively high density of PBZr in microsomal fractions remains to be elucidated.