Radiolabeled Ligands Specific for the G Protein‐Coupled State of Neurotensin Receptors

Abstract

Radiolabeled analogues of neuromedin N have been prepared by acylation of the α, ε1, and ε2 amino groups of [Lys2]neuromedin N (Lys‐Lys‐Pro‐Tyr‐Ile‐Leu) either with the 125I‐labeled Bolton‐Hunter reagent or with N‐succinimidyl[2,3‐3H]propionate. The binding properties of the purified analogues toward newborn mouse brain homogenate or toward membranes of cells transitorily (COS) or permanently (AA1) transfected with the cloned rat brain neurotensin receptor cDNA were evaluated and compared with those of radiolabeled neurotensin. The α‐modified analogue of [Lys2]neuromedin N behaves exactly like neurotensin in these binding experiments, whereas the ε1‐ and ε2‐modified analogues selectively recognize the fraction of neurotensin binding sites that is sensitive to GTPγS. The proportion of neurotensin receptors coupled to GTP binding proteins is ∼50% in membranes of newborn mouse brain or of AA1 cells that respond to neurotensin by an increase of the intracellular inositol trisphosphate concentration. By contrast, membranes of transitorily transfected COS cells that do not respond to neurotensin exhibit very low levels of GTP‐sensitive receptors labeled with the ε1‐ or ε2‐modified analogues. These radiolabeled peptides offer new tools to selectively detect active neurotensin receptors.

High‐affinity neurotensin receptors in the rat nucleus accumbens: Subcellular targeting and relation to endogenous ligand

“…The neurotensin antiserum that was used in our study maximally recognizes neurotensin but shows some cross reactivity with the related peptides neuromedin N and “lysine 8‐arginine 9‐neurotensin 10–13” (Bayer et al, 1991a). Neurotensin and neuromedin N are also processed from a common precursor in several limbic brain regions (Vincent, 1995; Gaudriault et al, 1996; Lu et al, 1996). Thus, the neurotensin labeling referred to above (see Results) may refer in part to neuromedin N as well as neurotensin.…”

In Vitro and In Vivo Hydrolytic Degradation Behaviors of a Drug-Delivery System Based on the Blend of PEG and PLA Copolymers

“…BEPO is a marketed in situ forming depot (ISFD) technology used to sustain the release of therapeutic agents through polymer-based long-acting-injectable (LAI) pharmaceutical forms. Drug products based on BEPO are formulated by dissolving a mixture of diblock (DB) methoxypoly­(ethylene glycol)- block -poly­( d , l -lactic acid) (mPEG–PLA) and triblock (TB) poly­( d , l -lactic acid)- block -poly­(ethylene glycol)- block -poly­( d , l -lactic acid) (PEG–PLA) copolymers in a biocompatible organic solvent . A drug substance is then incorporated into this mixture, solubilized or suspended.…”

“…Drug products based on BEPO are formulated by dissolving a mixture of diblock (DB) methoxypoly(ethylene glycol)- block -poly( d , l -lactic acid) (mPEG–PLA) and triblock (TB) poly( d , l -lactic acid)- block -poly(ethylene glycol)- block -poly( d , l -lactic acid) (PEG–PLA) copolymers in a biocompatible organic solvent. 1 A drug substance is then incorporated into this mixture, solubilized or suspended. Once injected into an aqueous environment, e.g.…”