Characterization of melatonin binding sites in the Harderian gland and median eminence of the rat
- Univ. of Seville School of Medicine, Sevilla (Spain)
The characterization of specific melatonin binding sites in the Harderian gland (HG) and median eminence (ME) of the rat was studied using ({sup 125}I)melatonin. Binding of melatonin to membrane crude preparations of both tissues was dependent on time and temperature. Thus, maximal binding was obtained at 37{degree}C after 30-60 min incubation. Binding was also dependent on protein concentration. The specific binding of ({sup 125}I)melatonin was saturable, exhibiting only the class of binding sites in both tissues. The dissociation constants (Kd) were 170 and 190 pM for ME and HG, respectively. The concentration of the binding sites in ME was 8 fmol/mg protein, and in the HG 4 fmol/mg protein. In competition studies, binding of ({sup 125}I)melatonin to ME or HG was inhibited by increasing concentration of native melatonin; 50% inhibition was observed at about 702 and 422 nM for ME and HG, respectively. Additionally, the ({sup 125}I)melatonin binding to the crude membranes was not affected by the addition of different drugs such as norepinephrine, isoproterenol, phenylephrine, propranolol, or prazosin. The results confirm the presence of melatonin binding sites in median eminence and show, for the first time, the existence of melatonin binding sites in the Harderian gland.
- OSTI ID:
- 5924749
- Journal Information:
- Life Sciences; (USA), Vol. 48:12; ISSN 0024-3205
- Country of Publication:
- United States
- Language:
- English
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RATS
TRACER TECHNIQUES
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ANIMALS
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KINETICS
MAMMALS
MEMBRANE PROTEINS
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ORGANIC NITROGEN COMPOUNDS
ORGANS
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550201* - Biochemistry- Tracer Techniques