Oocytes from Xenopus laevis contain an intrinsic sigma 2-like binding site.
In preparation for expression studies for rat brain sigma-binding sites, Xenopus oocytes were tested for the presence of [3H]di-o-tolylguanidine (DTG)-binding sites. Native oocytes were found to contain two intrinsic [3H]DTG-binding sites, a high-affinity site (Kd = 32 +/- 6 nM, Bmax of 45.7 +/- 19 pmol/mg protein) and a low-affinity binding site (Kd = 1.3 +/- 0.7 microM, Bmax of 3.2 +/- 0.7 nmol/mg protein). In a series of radioligand-binding-displacement studies, the high-affinity binding sites were found to have a binding profile which has a similar Kd to that of the mammalian sigma 2-binding site (32 vs. 38 nM). Comparison of the IC50 values for inhibition of [3H]DTG binding in rat liver and oocytes for DTG, haloperidol (HAL), (-)-pentazocine, (+)-3-(3-hydroxyphenyl)-N-propylpiperidine hydrochloride ((+)-3-PPP), (+)-pentazocine and Zn2+, showed similarity in rank (r2 = 0.913) but a 7-fold lower potency in oocytes. These results suggest that the high-affinity [3H]DTG-binding site in oocytes represents a sigma 2-like binding site.
Patterson
T A
TA
Department of Pharmacology, University of Washington, Seattle 98195.
Connor
M
M
Appleyard
S M
SM
Chavkin
C
C
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002227:Carbazoles / Q000378:metabolism; D003915:Dextromethorphan / Q000378:metabolism; D005260:Female; D006146:Guanidines / Q000378:metabolism; D006220:Haloperidol / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008454:Mazindol / Q000378:metabolism; D009865:Oocytes / Q000737:chemistry*; D010423:Pentazocine / Q000378:metabolism; D010620:Phenazocine / Q000031:analogs & derivatives / Q000378:metabolism; D010879:Piperazines / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017480:Receptors, sigma / Q000032:analysis* / Q000737:chemistry; D014982:Xenopus laevis / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
D002227:Carbazoles; D006146:Guanidines; D010879:Piperazines; D010880:Piperidines; D017480:Receptors, sigma; D003915:Dextromethorphan; C012134:SK&F 10047; C043425:vanoxerine; C044630:1-(2 (diphenylmethoxy)ethyl)-4-(3-phenylpropyl)piperazine; C026539:preclamol; C034931:rimcazole; D008454:Mazindol; D010620:Phenazocine; D015032:Zinc; D006220:Haloperidol; C050232:1,3-ditolylguanidine; D010423:Pentazocine