Figure 3.

Effect of reduced β-arrestin levels on second messenger generation. (A and B) Littermate WT (line 8) and βarr1-KO (line 6) cell lines (A) or littermate WT (line 1) and βarr2-KO (line 2) cell lines (B), as well as the βarr1/2-KO cell line 10, all expressing approximately100 fmol of β₂-AR per mg of protein, were stimulated with 10 μM isoproterenol as indicated. Isoproterenol-induced cAMP accumulation in the MEF lines was determined as the percent conversion of [³H]adenine into [³H]cAMP and then normalized to total forskolin (50 μM)-stimulated cAMP accumulation for each cell line. Data are the mean ± SEM of three to six experiments and were analyzed with GRAPHPAD PRISM software. (C) WT (line 1), βarr1-KO (line 6), βarr2-KO (line 2), and βarr1/2-KO (line 10) MEF cell lines, all expressing AT_1A-R at 200–350 fmol/mg of protein, were stimulated with 100 nM AngII for the indicated times. Accumulation of inositol phosphates was measured as the fold difference over basal accumulation. Data are the mean ± SEM of 10 experiments. Unpaired, two-tailed t tests were performed for total cAMP and total inositol phosphate accumulations between WT and βarr1-KO, βarr2-KO, or βarr1/2-KO lines (*, P < 0.005) and between βarr1/2-KO and βarr1-KO or βarr2-KO lines (†, P < 0.03).