%0 Journal Article %T Different patterns of agonist-induced modulation of ¦Á1B-adrenoceptor density at different initial expression levels %A Beilei Lei %A Qide Han %J Chinese Science Bulletin %@ 1861-9541 %D 2000 %I %R 10.1007/BF02886215 %X We compared the norepinephrine (NE) induced ¦Á1B-adrenoceptor (¦Á1B-AR) expression modulation between two transfected human embryonic kidney (MEK) 293 cell lines in which ¦Á1B-AR densities were (6 336 ¡À 913) and (773 ¡À 164) fmol mg1, respectively. Treatment of cells with NE (10 ¦Ìmol L1) for 48 h decreased high-level expressed ¦Á1B-AR density, but increased low-level expressed ¦Á1B-AR density. The protein kinase C inhibitor Calphostin C or Ro-31-8220 reversed, and its activator PMA mimicked the NE-induced down-regulation of high-level expressed ¦Á1B-AR. Moreover, PMA induced a down-regulation of low-level expressed ¦Á1B-AR. The endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (CPA) and the calcium chelator BAPTA/AM did not affect the down-regulation of high-level expressed ¦Á1B-AR, but inhibited the up-regulation of low-level expression ¦Á1B-AR induced by NE. These results suggest that ¦Á1B-adrenoceptor densities at different initial expression levels are differentially regulated by NE and their signal transduction pathways are different. %K ¦Á1B-adrenoceptor %K human embryonic kidney cells %K regulation %K signal transduction %U http://link.springer.com/article/10.1007/BF02886215