Fig. 5. Visualization of agonist-mediated internalization of ß1AR- and ß2AR-GFP. BHK cells stably expressing ß1AR-GFP (top row) or ß2AR-GFP (second row) or ß1AR-GFP and transiently co-expressing arrestin-2 (third row) or arrestin-3 (bottom row) were observed by confocal fluorescence microscopy during stimulation with 1 µM ISO for 0, 5, 10 and 20 minutes at 37°C as described in Materials and Methods. Whereas agonist treatment resulted in the redistribution of most of ß2AR-GFP from plasma membrane to large perinuclear vesicles, there was little redistribution of ß1AR-GFP until arrestin-2 or -3 was co-expressed. Under these conditions, most of ß1AR-GFP appeared in small, peripheral vesicles that were distinct from those containing ß2AR-GFP. Bar, 10 µm.