Use of 2-(/sup 125/I)iodomelatonin to characterize melatonin binding sites in chicken retina

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.84.11.3916· OSTI ID:6280234

Dubocovich, M L; Takahashi, J S

2-(/sup 125/I)Iodomelatonin binds with high affinity to a site possessing the pharmacological characteristics of a melatonin receptor in chicken retinal membranes. The specific binding of 2-(/sup 125/I)iodomelatonin is stable, saturable, and reversible. Saturation experiments indicated that 2-(/sup 125/I)iodomelatonin labeled a single class of sites with an affinity constant (Kd) of 434 +/- 56 pM and a total number of binding sites (Bmax) of 74.0 +/- 13.6 fmol/mg of protein. The affinity constant obtained from kinetic analysis was in close agreement with that obtained in saturation experiments. Competition experiments showed a monophasic reduction of 2-(/sup 125/I)iodomelatonin binding with a pharmacological order of indole amine affinities characteristic of a melatonin receptor: 2-iodomelatonin greater than 6-chloromelatonin greater than or equal to melatonin greater than or equal to 6,7-dichloro-2-methylmelatonin greater than 6-hydroxymelatonin greater than or equal to 6-methoxymelatonin much greater than N-acetyltryptamine greater than N-acetyl-5-hydroxytryptamine greater than 5-methoxytryptamine greater than 5-hydroxytryptamine (inactive). The affinities of these melatonin analogs in competing for 2-(/sup 125/I)iodomelatonin binding sites were correlated closely with their potencies for inhibition of the calcium-dependent release of (3H)dopamine from chicken and rabbit retinas, indicating association of the binding site with a functional response regulated by melatonin. The results indicate that 2-(/sup 125/I)iodomelatonin is a selective, high-affinity radioligand for the identification and characterization of melatonin receptor sites.

• Research Organization: Northwestern Univ. Medical School, Chicago, IL
• OSTI ID: 6280234
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 11; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIRDS
BODY
BODY AREAS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CELL CONSTITUENTS
CELL MEMBRANES
CHICKENS
DAYS LIVING RADIOISOTOPES
DOPAMINE
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EYES
FACE
FOWL
HEAD
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MELATONIN
MEMBRANE PROTEINS
MEMBRANES
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PHENOLS
POLYPHENOLS
PROTEINS
PYRROLES
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RETINA
SENSE ORGANS
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRYPTAMINES
VERTEBRATES