title: Localization and characterization of substance P binding sites in rat and rabbit eyes.
abstract: Specific and high-affinity binding sites for Substance P (SP) were found in eyes from albino rabbits and rats using an in vitro autoradiographic method with 125I-Bolton Hunter SP (BHSP). autoradiograms were generated by apposing 10-20 microns-thick cryostat eye sections to 3H-Hyperfilm or liquid emulsion and quantified by means of image-analysis procedures. Kinetic studies showed that equilibrium was reached after a 75-min incubation at room temperature. In rat retina, specific binding corresponding to approximately 90% of total binding, was reversible, of high affinity (dissociation constant [Kd], 0.13 +/- 0.02 nM). Half-time for dissociation of 125I-BHSP was about 15 min. Unlabeled SP and the two neurokinins (NK) A and B competed in a concentration-dependent manner for retinal sites labeled by 125I-BHSP with the following order of potencies: SP greater than NKA greater than NKB, in agreement with a pharmacologic profile of a SP receptor site. In both species, specific binding was found in the iris sphincter muscle, choroid, and retina. In rats, detectable amounts of SP-binding sites were also expressed in the corneal epithelium and iridial stroma. Quantitative analysis of the autoradiograms revealed that the highest densities of 125I-BHSP binding sites were localized in the iris sphincter muscle in rabbits and the inner retina in rats.
authors.affiliation: INSERM U55, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Denis
authors.forename: V
authors.initials: V
authors.lastname: Fardin
authors.forename: J P
authors.initials: JP
authors.lastname: Nordmann
authors.forename: P P
authors.initials: PP
authors.lastname: Elena
authors.forename: L
authors.initials: L
authors.lastname: Laroche
authors.forename: H
authors.initials: H
authors.lastname: Saraux
authors.forename: W
authors.initials: W
authors.lastname: Rostene
mesh_terms: D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D005123:Eye / Q000378:metabolism*; D007700:Kinetics; D015287:Neurokinin B / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*
chemical_list: D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter; D013373:Substance P; D015287:Neurokinin B