Binding and Functional Affinity of Sarpogrelate, Its Metabolite M-1 and Ketanserin for Human Recombinant Alpha-1-Adrenoceptor Subtypes

Abstract

Serotonin (5-HT₂) antagonists show high affinity for the α₁-adrenoceptor (α₁-AR) in addition to the 5-HT₂ receptor. In the present study we compared the pharmacological characteristics of a new 5-HT₂ antagonist sarpogrelate and its active metabolite M-1 with those of ketanserin on human recombinant α₁-AR subtypes. In the binding study, sarpogrelate, M-1 and ketanserin produced concentration-dependent inhibition of ³H-prazosin binding to α₁-ARs. Among the three drugs, ketanserin showed the highest affinity for α_1a-, α_1b- and α_1d-ARs (pKi 8.0, 8.3 and 7.6, respectively). Sarpogrelate had a relatively low affinity for the three subtypes (6.3 , 6.4 and 6.3, respectively) and M-1 showed medium affinity (7.1, 7.1 and 6.1, respectively). Chinese hamster ovary (CHO) cells expressing each α₁-AR subtype showed concentration-dependent inositol phosphate (IP) accumulation in response to phenylephrine. The concentration response curves were shifted to the right by three drugs, and the pKb values were close to the pKi values in the binding study. In addition to these effects, sarpogrelate and M-1, but not ketanserin produced an increase in the basal IP level of α_1d-expressed CHO cells, although the increase was less than that of phenylephrine. The present results indicate that sarpogrelate and M-1 have antagonistic activity to the three α₁-AR subtypes, but their affinities are significantly lower than those of ketanserin.

Differential Roles of 5-HT Receptor Subtypes in Cue and Cocaine Reinstatement of Cocaine-Seeking Behavior in Rats

“…Therefore, the effect of ketanserin may result from its action of blocking 5-HT 2A receptors, an action that may predominate given that ketanserin has a higher affinity for 5-HT 2A receptors relative to 5-HT 2C and 5-HT 2B receptor subtypes (pK i ¼ 8.9, 7.0, and 5.4, respectively; Baxter et al, 1995). Alternatively, it is possible that a-adrenergic receptors may be involved in the attenuation of cue reinstatement since ketanserin also has affinity for these receptors (pK i ¼ 8.0, 8.3, and 7.6 for a-1a, 1b, and 1c, respectively; Israilova et al, 2002). Further research is needed to investigate these possibilities.…”

Pharmacological Characterization and Cross Talk of α1A- and α1B-Adrenoceptors Coexpressed in Human Embryonic Kidney 293 Cells

“…HEK 293 cells stably expressing ␣ 1A -, ␣ 1B -, and coexpressing both AR subtypes were seeded in collagen-coated 24-well plates (ϳ1 ϫ 10 5 cells/well) 24 h before each experiment. As reported previously (Israilova et al, 2002), cells were then washed twice with inositol-free Dulbecco's modified Eagle's medium without serum (fetal bovine serum) and labeled for 24 h with […”

Asp125 and Thr130 in Transmembrane Domain 3 Are Major Sites of .ALPHA.1b-Adrenergic Receptor Antagonist Binding

“…13) In briefly, after labeling, cells were washed twice with Krebs Hensleit (KHL) buffer to remove unincorporated radioactivity. Then, cells were preincubated for 15 min in KHL buffer with 10 mmol/l LiCl in the presence or absence of tested drugs and various concentration of phenylephrine of 45 min.…”