2( sup 125 I)Iodomelatonin binding sites in spleens of guinea pigs

Journal Article · Wed Jan 01 00:00:00 EST 1992 · Life Sciences; (United States)

DOI:https://doi.org/10.1016/0024-3205(92)90427-Q· OSTI ID:5378558

Poon, A M.S. ^[1]; Pang, S F ^[2]

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1. Univ. of Hong Kong, (Hong Kong)
2. Clarke Inst. of Psychiatry, Toronto, Ontario (Canada)

2-({sup 125}I)Iodomelatonin was found to bind specifically to the membrane preparations of the spleens of guinea pigs with high affinity. The binding was rapid, stable, saturable and reversible. Scatchard analysis of the binding assays revealed an equilibrium dissociation constant (Kd) of 49.8{plus minus}4.12 pmol/l and binding site density (Bmax) of 0.69{plus minus}0.082 fmol/mg protein at mid-light. There was no significant change in the Kd or the Bmax at mid-dark. Kinetic analysis showed a Kd of 23.13{plus minus}4.81 pmol/l, in agreement to that derived from the saturation studies. The 2-({sup 125}I)iodomelatonin binding sites have the following order of potency: 2-iodomelatonin > melatonin > 6-chloromelatonin {much gt} N-acetylserotonin, 6-hydroxymelatonin > 5-methoxytryptamine, 5-methoxytryptophol > serotonin, 5-methoxyindole-3-acetic acid > 5-hydroxytryptophol, 3-acetylindole, 1-acetylindole-3-carboxyaldehyde, L-tryptophan > tryptamine, 5-hydroxyindole-3-acetic acid. Differential centrifugation studies showed that the binding sites are localized mainly in the nuclear fraction, the rest are distributed in the microsomal fraction, mitochondrial fraction and cytosolic fraction. The demonstration of 2-({sup 125}I)iodomelatonin binding sites in the spleen suggests the presence of melatonin receptors and a direct mechanism of action of melatonin on the immune system.

• OSTI ID: 5378558
• Journal Information: Life Sciences; (United States), Vol. 50:22; ISSN 0024-3205
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MELATONIN
RECEPTORS
TISSUE DISTRIBUTION
AFFINITY
BIOCHEMICAL REACTION KINETICS
CELL MEMBRANES
GUINEA PIGS
IODINE 125
MITOCHONDRIA
SPLEEN
TRACER TECHNIQUES
AMINES
ANIMALS
AROMATICS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
ELECTRON CAPTURE RADIOISOTOPES
HETEROCYCLIC COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
PYRROLES
RADIOISOTOPES
REACTION KINETICS
RODENTS
TRYPTAMINES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques