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The expression levels of 3 subtypes (α1A, α1B and α1D) of α1-adrenoceptor have been determined by radioligand binding assay and reverse-transcription polymerase chain reaction (RT-PCR) assay in neonatal rat heart. mRNAs for all the 3 subtypes have been detected in RT-PCR assays. The density of total α1-AR ( Bmax) was (134±4) fmol/mg protein and the Kd value was (164 ± 15) pmol/L. The α1-adrenoceptor subtypes selective antagonists, RS17053, ( + )niguldipine, 5-MU, BMY 7378 and WB4101, competitively inhibited binding of 125I-BE 2254 to α1-adrenoceptor in a concentration-dependent manner. The inhibition curves were better fit for the two-site model. The binding sites for α1A-, α1B- and α1D-adrenoceptor amounted to 25% , 50% and 25% of the total binding sites, respectively.
The expression levels of 3 subtypes (α1A, α1B and α1D) of α1-adrenoceptor have been determined by radioligand binding assay and reverse-transcription polymerase chain reaction (RT-PCR) assay in neonatal rat heart. MRNAs for all the 3 subtypes have been The density of total α1-AR (Bmax) was (134 ± 4) fmol / mg protein and the Kd value was (164 ± 15) pmol / L. The α1-adrenoceptor subtypes selective antagonists, RS17053 , (+) niguldipine, 5-MU, BMY 7378 and WB4101, competitively inhibited binding of 125I-BE 2254 to α1-adrenoceptor in a concentration- dependent manner. The inhibition curves were better fit for the two-site model. The binding sites for α1A-, α1B- and α1D-adrenoceptor amounted to 25%, 50% and 25% of the total binding sites, respectively.