Characterization of histamine H(2)-like receptors in duck cerebral cortical membranes by [(3)H]tiotidine binding.
A selective (according to mammalian criteria) histamine (HA) H(2)-receptor radioligand [(3)H]tiotidine ([(3)H]TIOT) was used to characterize HA receptors in duck cerebral cortex by an in vitro binding technique. The specific binding of [(3)H]TIOT to duck cerebral cortical membranes was found to be rapid, stable, saturable, reversible, and of high affinity. Saturation analysis resulted in a linear Scatchard plot suggesting binding to a single class of receptor binding sites with high affinity (K(d)=19.5 nM) and high capacity (B(max)=356 fmol/mg protein). Competition studies showed the following relative rank order of potency of various HA receptor ligands to inhibit the [(3)H]TIOT binding: antagonists, tiotidine>>ranitidine=zolantidine>or=cimetidine>>mepyramine>thioperamide; agonists, HA>or=4-methylHA>2-methylHA>dimaprit>>R(alpha)-methylHA. The biphasic nature of the displacement curve for HA and the effect of 5'-guanylimidodiphosphate indicate the coupling of the studied receptor to G-protein. It is suggested that HA receptors in the duck cerebral cortex labelled with [(3)H]TIOT represent either avian-specific H(2)-like HA receptors or a novel subtype of HA receptors, coupled to a signalling pathway other than the adenylyl cyclase/cyclic adenosine monophosphate one.
Zawilska
Jolanta B
JB
Department of Pharmacodynamics, Medical University of Lódź, Poland. jolantaz@amina1.zabpan.lodz.pl
Zalewska-Kaszubska
Jadwiga
J
Przybysz
Marzena
M
Nowak
Jerzy Z
JZ
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism*; D002927:Cimetidine / Q000031:analogs & derivatives* / Q000378:metabolism*; D004372:Ducks / Q000378:metabolism*; D005260:Female; D006635:Histamine H2 Antagonists / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008566:Membranes / Q000378:metabolism; D011970:Receptors, Histamine H2 / Q000378:metabolism*; D014316:Tritium
D006635:Histamine H2 Antagonists; D008024:Ligands; D011970:Receptors, Histamine H2; D014316:Tritium; D002927:Cimetidine; C023990:tiotidine