A highly sensitive and selective radioimmunoassay for the measurement of neurotensin

A highly selective and sensitive radioimmunoassay (RIA) for the detection o f endogenous neurotensin (NT) has been developed. We have raised a C-termin ally-directed antibody (CAb) that specifically binds 'biologically active' NT (NT and NT8-13) and that does not significantly cross-react with inactiv e NT metabolites or other bioactive peptides in the CNS. By reducing the vo lume of the assay to a low volume-RIA (30 mu l), such that in vivo measurem ents can be made, we have increased the sensitivity (< 0.3 fmol per tube), With inter- and intra-assay variations of 11.2 and 5.8%, respectively. Comp arisons with similar methods of detecting NT have demonstrated that this RI A has a higher sensitivity than previously used RIA's and ELISA's. The data presented suggests that this sensitive RIA is a reliable method ideal for the detection of small quantities of biologically active NT. (C) 2000 Publi shed by Elsevier Science B.V.