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.
School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
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Burcher
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Badgery-Parker
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Zeng
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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