Characterization of non-opioid [3H]dynorphin A-(1-13) binding sites in the rat heart.
The binding characteristics of [3H]Dynorphin A-(1-13) ([3H]Dyn A-(1-13) were examined in membrane preparations of rat heart. Saturation binding studies with increasing concentrations between 2.5 and 500 nM indicated that [3H]Dyn A-(1-13) binds to a single population of sites with a Kd of 285 nM and a Bmax of 215 pmol/mg protein. [3H]Dyn A-(1-13) binding is sensitive to trypsin treatment and it is inhibited by Zn2+ and Mg2+ with IC50 values of 159 and 310 microM, respectively. Dyn A and related peptides competes with the binding of [3H]Dyn A-(1-13) with the following order of potency: Dyn A-(1-13) > Dyn A > Dyn B > alpha-neo-endorphin > Dyn A-(1-8). The non-opioid peptides Dyn A-(2-13), Dyn A-(3-13) and Dyn A-(5-13) are as potent (Ki of 0.35, 0.44 and 0.59 microM, respectively) as Dyn A-(1-13) (Ki of 0.36 microM) in inhibiting [3H]Dyn A-(1-13) binding while Leu-enkephalin (Leu-Enk) exhibits no inhibitory effect at 100 microM. Selective ligands for kappa (kappa: U-50,488H, U-69,593), mu (mu: [D-Ala2, MePhe4, Glyol5]Enk) and delta (delta: [D-Ser2, Thr6]Leu-Enk) opioid receptors as well as for phencyclidine (PCP: MK-801, TCP) and sigma (sigma: (+)-SKF-10047, DTG, 3(+)-PPP) receptors show little or no inhibition of [3H]Dyn A-(1-13) binding at 100 microM. These results indicate that the heart contains a low affinity high capacity binding site for Dyn A and related peptides, distinct from opioid, PCP and sigma receptors.
Dumont
M
M
Department of Pharmacology, Faculty of Medicine, University of Ottawa, Ontario, Canada.
Lemaire
S
S
D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001667:Binding, Competitive / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D004399:Dynorphins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D007700:Kinetics; D015636:Magnesium Chloride / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009019:Morphinans / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012680:Sensitivity and Specificity; D017967:Zinc Compounds / Q000494:pharmacology
D002712:Chlorides; D009019:Morphinans; D010446:Peptide Fragments; D010455:Peptides; D011956:Receptors, Cell Surface; D017967:Zinc Compounds; D015636:Magnesium Chloride; C026843:dynorphin (1-13); D004399:Dynorphins; C016837:zinc chloride