RT Journal Article SR Electronic T1 Expression of α-Adrenoceptor Subtypes by Smooth Muscle Cells and Adventitial Fibroblasts in Rat Aorta and in Cell Culture JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 441 OP 452 VO 298 IS 2 A1 James E. Faber A1 Nengyu Yang A1 Xiaohua Xin YR 2001 UL http://jpet.aspetjournals.org/content/298/2/441.abstract AB Previous radioligand binding reports of vascular α-adrenoceptor (AR) density have been limited to total α1- or α2-ARs. Studies using whole blood vessel homogenates have not differentiated among receptor or mRNA expression by medial smooth muscle cells (SMCs) versus adventitial fibroblasts (AFBs). Therefore, we used quantitative reverse transcription-polymerase chain reaction and radioligand binding to measure α-AR subtypes in media, adventitia, and cultured SMCs and AFBs from rat aorta. Both media and adventitia expressed α1A-, α1B-, α1D-, and α2D-AR mRNAs, but in markedly different abundances. Total α1-AR density was the same for media and adventitia (Bmax = 101 ± 10 versus 96 ± 16 fmol/mg of protein). However, densities for α1A-, α1B-, and α1D-AR subtypes in media were 19 ± 2, 26 ± 4, and 55 ± 2%, and in adventitia were 44 ± 3, 37 ± 5, and 19 ± 2%. No α2B- or α2C-AR transcripts were detected in either layer or in cultured SMCs or AFBs. Total α1-AR densities in cultured SMCs and AFBs (Bmax = 111 ± 4 and 48 ± 6 fmol/mg of protein, respectively) were similar to media and adventitia, with α1B- and α1D-AR transcript levels and receptors largely sustained. However, α1A- and α2D-AR expression in cultured SMCs and AFBs was strongly reduced, compared with media and adventitia, an effect not prevented by 30 different culture conditions. Like SMCs, exposure of AFBs to norepinephrine induced protein synthesis and proliferation of AFBs. This is the first study to quantitate α-AR subtype expression in media and adventitia and in cultured SMCs and AFBs. In addition, we report the intriguing finding that AFBs express α1-ARs in similar abundance as medial SMCs and that norepinephrine induced them to proliferate. The American Society for Pharmacology and Experimental Therapeutics