Characterisation of a novel, selective radioligand, [125I][Lys5,Tyr(I2)7,MeLeu9,Nle10]neurokinin A-(4-10), for the tachykinin NK2 receptor in rat fundus.
The tyrosyl derivative of the tachykinin NK2 selective agonist [Lys5,MeLeu9,Nle10]NKA-(4-10) was iodinated and the product [125I][Lys5,Tyr(I2)2,MeLeu9,Nle10]NKA-(4-10) purified using reverse phase HPLC. The binding characteristics of this novel radioligand were investigated in homogenates of rat gastric fundus. Binding was saturable, reversible and to a single population of high affinity sites of KD 1.3 +/- 0.2 nM (n = 4). Specific binding of [125I][Lys5,Tyr(I2)7,MeLeu9,Nle10]NKA-(4-10) was inhibited by neuropeptide gamma SR 48968 > or = neurokinin A (NKA) > or = [Lys5,MeLeu9,Nle10]NKA-(4-10) > [Lys5,Tyr7,MeLeu9,Nle10] NKA-(4-10) > neuropeptide K > [Lys5,Tyr(I2)7,MeLeu9,Nle10]NKA-(4-10) > MDL 29,913 > [127I]- Bolton-Hunter-NKA > neurokinin B > substance P (SP) >> MEN 10207 > [Sar9,Met(O2)11]SP >> senktide, indicating binding to NK2 receptors. NKA, [Lys5,MeLeu9,Nle10]NKA-(4-10) and [Lys5,Tyr(I2)7,MeLeu9,Nle10]NKA-(4-10) contracted the isolated fundus strip, with pD2 values 7.9, 7.7 and 7.4, respectively. This novel, highly selective radioligand should prove useful in characterisation studies in peripheral tissues.
Burcher
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School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
Badgery-Parker
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Zeng
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Lavielle
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D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005748:Gastric Fundus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D015288:Neurokinin A / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter / Q000187:drug effects* / Q000378:metabolism
D010446:Peptide Fragments; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter; C080627:neurokinin A (4-10), Lys(5)-Tyr(I2)(7)-MeLeu(9)-Nle(10)-; D015288:Neurokinin A