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Article: 2[125I]iodomelatonin binding sites in guinea pig platelets

Title2[125I]iodomelatonin binding sites in guinea pig platelets
Authors
KeywordsAdenosine diphosphate
Anti-MT1
Arachidonic acid
Pineal
Platelet aggregation
Issue Date2002
PublisherBlackwell Munksgaard. The Journal's web site is located at http://www.blackwellpublishing.com/journals/JPI
Citation
Journal Of Pineal Research, 2002, v. 32 n. 2, p. 97-105 How to Cite?
AbstractUsing 2[125I]iodomelatonin as the radioligand, we characterized 2[125I]iodomelatonin binding sites in guinea pig platelet membrane preparations. Saturation radioreceptor studies indicated that these 2[125I]iodomelatonin binding sites were of picomolar affinity and femtomolar density. The dissociation constant (Kd) and maximum number of receptor sites (Bmax) were 42.5 ± 1.79 pM and 11.8 ± 0.8 fmol/mg protein (n = 6), respectively. 2[125I]Iodomelatonin competition studies with indoles or drugs indicate the following rank order of potency: 2-iodomelatonin > melatonin ≥ 6-chloromelatonin > 6-hydroxymelatonin > N-acetylserotonin > 5-methoxytryptophol, whereas serotonin and its analogs had less than 20% inhibition at 0.1 mM, Guanosine 5′-O-(3-thiotriphosphate) significantly increased the Kd by twofold suggesting that these binding sites are coupled to the guanine nucleotide binding proteins. Immunoblotting studies using anti-MT1 IgG demonstrated one peptide blockable band with an apparent molecular mass of 37 kDa. Melatonin had no effect on prostacyclin or forskolin-stimulated intracellular 3′,5′-cyclic adenosine monophosphate accumulation. A diurnal variation in binding density, which was abolished after the animals were adapted to constant light conditions, was observed, Age related studies demonstrated that Bmax increased as the animal matured. Physiological melatonin concentrations potentiated whereas those at pharmacological levels inhibited adenosine diphosphate- or arachidonic acid-stimulated platelet aggregation. Our study demonstrated G-protein coupled, saturable, reversible and highly specific picomolar affinity 2[125I]iodomelatonin binding sites in guinea pig platelets. Pharmocological and physiological data indicate that they may be different from the nanomolar [3H]melatonin binding sites in human platelets previously reported.
Persistent Identifierhttp://hdl.handle.net/10722/81346
ISSN
2015 Impact Factor: 9.314
2015 SCImago Journal Rankings: 2.655
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorYau, MYCen_HK
dc.contributor.authorPang, CSen_HK
dc.contributor.authorKravtsov, Gen_HK
dc.contributor.authorPang, SFen_HK
dc.contributor.authorShiu, SYWen_HK
dc.date.accessioned2010-09-06T08:16:36Z-
dc.date.available2010-09-06T08:16:36Z-
dc.date.issued2002en_HK
dc.identifier.citationJournal Of Pineal Research, 2002, v. 32 n. 2, p. 97-105en_HK
dc.identifier.issn0742-3098en_HK
dc.identifier.urihttp://hdl.handle.net/10722/81346-
dc.description.abstractUsing 2[125I]iodomelatonin as the radioligand, we characterized 2[125I]iodomelatonin binding sites in guinea pig platelet membrane preparations. Saturation radioreceptor studies indicated that these 2[125I]iodomelatonin binding sites were of picomolar affinity and femtomolar density. The dissociation constant (Kd) and maximum number of receptor sites (Bmax) were 42.5 ± 1.79 pM and 11.8 ± 0.8 fmol/mg protein (n = 6), respectively. 2[125I]Iodomelatonin competition studies with indoles or drugs indicate the following rank order of potency: 2-iodomelatonin > melatonin ≥ 6-chloromelatonin > 6-hydroxymelatonin > N-acetylserotonin > 5-methoxytryptophol, whereas serotonin and its analogs had less than 20% inhibition at 0.1 mM, Guanosine 5′-O-(3-thiotriphosphate) significantly increased the Kd by twofold suggesting that these binding sites are coupled to the guanine nucleotide binding proteins. Immunoblotting studies using anti-MT1 IgG demonstrated one peptide blockable band with an apparent molecular mass of 37 kDa. Melatonin had no effect on prostacyclin or forskolin-stimulated intracellular 3′,5′-cyclic adenosine monophosphate accumulation. A diurnal variation in binding density, which was abolished after the animals were adapted to constant light conditions, was observed, Age related studies demonstrated that Bmax increased as the animal matured. Physiological melatonin concentrations potentiated whereas those at pharmacological levels inhibited adenosine diphosphate- or arachidonic acid-stimulated platelet aggregation. Our study demonstrated G-protein coupled, saturable, reversible and highly specific picomolar affinity 2[125I]iodomelatonin binding sites in guinea pig platelets. Pharmocological and physiological data indicate that they may be different from the nanomolar [3H]melatonin binding sites in human platelets previously reported.en_HK
dc.languageengen_HK
dc.publisherBlackwell Munksgaard. The Journal's web site is located at http://www.blackwellpublishing.com/journals/JPIen_HK
dc.relation.ispartofJournal of Pineal Researchen_HK
dc.subjectAdenosine diphosphateen_HK
dc.subjectAnti-MT1en_HK
dc.subjectArachidonic aciden_HK
dc.subjectPinealen_HK
dc.subjectPlatelet aggregationen_HK
dc.title2[125I]iodomelatonin binding sites in guinea pig plateletsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0742-3098&volume=32&spage=97&epage=105&date=2002&atitle=2[125I]Iodomelatonin+binding+sites+in+guinea+pig+plateletsen_HK
dc.identifier.emailShiu, SYW: sywshiu@hkucc.hku.hken_HK
dc.identifier.authorityShiu, SYW=rp00384en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1034/j.1600-079x.2002.1822.xen_HK
dc.identifier.pmid12071474en_HK
dc.identifier.scopuseid_2-s2.0-0036010074en_HK
dc.identifier.hkuros72041en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0036010074&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume32en_HK
dc.identifier.issue2en_HK
dc.identifier.spage97en_HK
dc.identifier.epage105en_HK
dc.identifier.isiWOS:000174715900005-
dc.publisher.placeDenmarken_HK
dc.identifier.scopusauthoridYau, MYC=7006864967en_HK
dc.identifier.scopusauthoridPang, CS=7201425191en_HK
dc.identifier.scopusauthoridKravtsov, G=7003811092en_HK
dc.identifier.scopusauthoridPang, SF=7402528719en_HK
dc.identifier.scopusauthoridShiu, SYW=7005550655en_HK

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