Effects of dimethylbenz[a]anthracene-induced malignancy on the subcellular distribution of peripheral benzodiazepine receptors in submandibular glands of rats.

The binding of [3H]Ro 5-4864 to peripheral benzodiazepine receptors (PBRs) was studied in normal and malignant submandibular glands of rats. The carcinoma was induced by implantation of 7,12-dimethylbenz[a]anthracene (DMBA) into the glands. [3H]Ro 5-4864 binding to normal and malignant submandibular glands indicated one population of binding sites with high affinity (KD of 3.4 and 4.4 nM for normal and malignant respectively) and saturability (Bmax) of 487 and 321 pmol/g tissue for normal and malignant respectively). Subcellular localization of PBRs indicates that mitochondria was the primary locale of the receptor in both cases and the decrease in Bmax was due primarily to a decrease in the binding capacity of PBRs in mitochondria.