Kappa opioid binding sites on the R1.1 murine lymphoma cell line: sensitivity to cations and guanine nucleotides.
The present study describes the characterization of an opioid binding site on membranes prepared from the R1.1 cell line, a murine thymoma. Specific (-)[3H]bremazocine binding was saturable, stereoselective, and limited to a single high affinity binding site with a Kd value of 15.2 +/- 1.6 pM and a Bmax value of 54.8 +/- 6.0 fmol/mg of protein. The kappa-selective alkaloids and dynorphin peptides inhibited (-)[3H]bremazocine binding with Ki values of less than 1 nM, in contrast to mu- and delta-selective ligands. The high affinity of this site for alpha-neo-endorphin and U50,488 suggests that this kappa opioid binding site resembles the kappa 1b subtype. NaCl, as well as other mono- and divalent cations, inhibited (-)[3H]bremazocine binding. In the presence of NaCl, the nucleotides GTP, GDP, and the nonhydrolyzable analog guanylyl-5'-imidodiphosphate (Gpp(NH)p) also decreased (-)[3H]bremazocine binding, suggesting that this kappa opioid binding site is coupled to a G-protein. In summary, R1.1 cells possess a single high affinity kappa opioid receptor that shares many properties with brain kappa 1b opioid receptors.
Lawrence
D M
DM
Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, NY 14642.
Bidlack
J M
JM
D000818:Animals; D001575:Benzomorphans / Q000378:metabolism; D001665:Binding Sites; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008223:Lymphoma / Q000378:metabolism*; D051379:Mice; D017473:Receptors, Opioid, kappa / Q000032:analysis* / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D001575:Benzomorphans; D006150:Guanine Nucleotides; D017473:Receptors, Opioid, kappa; D006165:Guanylyl Imidodiphosphate; D012965:Sodium Chloride; C027248:bremazocine