Localization of peripheral benzodiazepine binding sites and diazepam-binding inhibitor (DBI) mRNA in mammary glands and dimethylbenz(α)antracene (DMBA)-induced mammary tumors in the rat

Abstract

An association of diazepam-binding inhibitor (DBI), an endogenous ligand at the benzodiazepine (BZD) receptor, with the peripheral type BDZ receptor (PBR) has been reported in the brain and a few peripheral tissues. In order to verify whether or not DBI and PBR are present in the mammary tissue, we have proceeded to the localization of DBI mRNA and PBR in rat mammary glands and DMBA-induced mammary tumors. DBI mRNA was detected by in situ hybridization using a 35S-labelled single-stranded RNA probe complementary to DBI mRNA and PBR by in vitro autoradiography using [ 3H]PK11195 as the ligand. In mammary glands from virgin and lactating animals, both DBI mRNA and PBR were detected in acinar cells. In dimethylbenz(α)anthracene (DMBA)-induced tumors, hybridization signal was not detected in all the cells whereas PBR appeared to be present in all the tumoral cells, although non uniformly distributed. These data indicating that mammary DMBA-induced tumoral cells contain both DBI and PBR suggest that BZD receptors might be involved in the regulation of mammary glands as well as mammary tumoral cells.