Effects of β2R knockdown in AH43a and AH45b. (A) RT-PCR of β2R expression in NT control and ADRB2 KO (sgADRB2) in AH43a and AH45b, using β-actin as endogenous control. (B) MTT assay of NT control and ADRB2 KO (sgADRB2) in AH43a (n = 6) and AH45b (n = 12) treated with isoproterenol. Data are representative of two independent experiments. P values were determined by Student’s t test. *P < 0.5, **P < 0.01, ns: not significant.