Functional assessment and partial characterization of [3H](+)-pentazocine binding sites on cells of the immune system

The existence of sigma receptors on lymphocytes and thymocytes was characterized using [3H](+)-pentazocine. [3H](+)-Pentazocine specifically labels high affinity sigma-type binding sites on T- and B-enriched lymphocyte membranes. The binding is saturable with T lymphocyte sites having a KD value of 401 +/- 85 nM and B lymphocyte sites having a KD value of 302 +/- 46 nM. Likewise, saturable high (KD1 277 +/- 92 nM) and low (KD2 2.5 +/- 1.2 microM) affinity sites for [3H](+)-pentazocine are found on thymocytes as well. In competition studies with lymphocytes, the rank order of potency for competing ligands is (+)-pentazocine = N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2- (1-pyrrolidinyl)ethylamine (BD1008) greater than 1R,2S-(+)-cis-N-(2-(3,4-dichlorophenyl)ethyl]-2- (1-pyrrolidinyl)cyclohexylamine (LR132) greater than or equal to (-)-pentazocine greater than or equal to phenazocine greater than (+/-)-trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulphonate (U-50,488H) = phencyclidine greater than haloperidol = 1,3-di- (o)-tolylguanidine. In competition studies with thymocytes, the rank order of potency for competing ligands is (+)-pentazocine = BD1008 greater than or equal to phenazocine greater than haloperidol greater than 1,3-di-(o)-tolylguanidine greater than phencyclidine greater than (-)-pentazocine. These compounds were also investigated as potential regulatory molecules in mitogen-stimulated lymphocyte proliferation assays. Of the compounds tested, phencyclidine, 1,3-di-(o)-tolylguanidine, haloperidol, and (+)-pentazocine suppress concanavalin A-induced proliferation at high (10(-5) M) concentrations while (-)-pentazocine is inactive. When pokeweed mitogen or lipopolysaccharide are used, these compounds enhance or suppress lymphocyte proliferation depending on the mitogen and concentration of ligand. These results indicate a stereoselective receptor for (+)-pentazocine which is coupled to biological processes of lymphocytes.