Peripheral benzodiazepine receptor in human endometrium and endometrial carcinoma

Since elevated concentrations of peripheral benzodiazepine (PBZr) have been reported in some tumors it was of interest to study the distribution PBZr in the endometrium and endometrial carcinoma. A specific ligand or PK 11195 was used to measure PBZr in the mitochondria (m-fraction) and the microsomal fraction (p-fraction). Density of binding sites and binding affinity (KD) was computed from Scatchard analysis. Binding in both m- and p-fractions from endometrium and endometrial carcinoma were saturable and of high affinity. The PBZr density in p-fraction from endometrium was slightly higher than in m-fraction, whereas the binding in m-fraction in endometrial carcinoma was more than 2-fold higher than in p-fraction. The difference between the densities in m-fraction from endometrial cancer and endometrium was highly significant (p < 0.005). 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 and could be of diagnostic and/or therapeutic value in endometrial cancer. The role of a relatively high density of PBZr in microsomal fractions remains to be elucidated.