Figure 1.

Up-regulation of receptor density and reduction of inositol phosphates accumulation by a range of alpha-1 AR antagonists. In (A) sustained treatment with antagonists resulted in up-regulation of the mutant receptor but not the wild-type receptor. CHO clones were treated for 72 h with no drug or with 100 nM of prazosin, KMD-3213, BMY7378, WB4101, phentolamine or HV723. Cells were extensively washed to remove the antagonist and receptor density was estimated in the binding study with [³H]-prazosin as outlined under Methods. Results are presented as the means±s.e.mean for three sets of experiments. In (B) CHO cells expressing the mutant were treated with 100 nM drugs as in (A) and accumulated inositol phosphates in the presence of LiCl was measured as described in Methods. The value of scintillation counts of inositol phosphates in mock cells without antagonist (8600±100 d.p.m.) was subtracted from those of other preparations. Resulting values were normalized against that in CHO cells expressing the mutant receptor without antagonist treatment (3400±100 d.p.m.). All antagonists except KMD-3213 produced significant (P<0.05) changes in values from that of cells without drug treatment in both assays.