Proctolin antagonists bind to [ 3H]proctolin binding sites in the locust hindgut

Proctolin caused dose-dependent (1–200 nM) contraction of the isolated hindgut of S. gregaria which was abolished by [α-methyl-L-tyrosine 2]-proctolin (1 μM). In comparison, cycloproctolin (5 μM) reduced the proctolin maximum response by 41%. Hindgut homogenates contained [ 3H]proctolin binding site...

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Bibliographic Details
Published in:Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2000-02, Vol.21 (2), p.189-196
Main Authors: Gray, A.S, Hancock, J.T, Osborne, R.H
Format: Article
Language:English
Subjects:
Animals
Binding
Binding Sites
Bioassay
Grasshoppers - drug effects
In Vitro Techniques
Intracellular Membranes - drug effects
Intracellular Membranes - metabolism
Kinetics
Neuropeptide
Neuropeptides
Neurotransmitter Agents - pharmacology
Neurotransmitter Uptake Inhibitors - pharmacology
Oligopeptides - antagonists & inhibitors
Oligopeptides - pharmacology
proctolin
Proctolin antagonists
Receptor
Schistocerca
Schistocerca gregaria
Tritium
Viscera - drug effects
Viscera - metabolism
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Summary:Proctolin caused dose-dependent (1–200 nM) contraction of the isolated hindgut of S. gregaria which was abolished by [α-methyl-L-tyrosine 2]-proctolin (1 μM). In comparison, cycloproctolin (5 μM) reduced the proctolin maximum response by 41%. Hindgut homogenates contained [ 3H]proctolin binding sites with a K d value of 660 nM, a B max value of 23.8 pmol/mg protein and a Hill coefficient of 0.934. Cycloproctolin (IC 50, 220 nM; K i, 204 nM), unlabeled proctolin (IC 50 680 nM) and [α-methyl-L-tryosine 2]-proctolin (IC 50 3.1 μM, K i , 2.9 μM) but not SchistoFLRFamide (1 nM–10 μM) were capable of displacing bound [ 3H]proctolin.
ISSN:0196-9781
1873-5169
DOI:10.1016/S0196-9781(99)00199-0