Cardiac dysfunction in TNFα-Tg mice is associated with βAR desensitization (A) Cardiac lysates from Wt and TNFα-Tg mice 6 or 20 weeks of age were immunoblotted for GRK 2, 3, 5, 6, phospho-β2AR and adenylyl cyclase V/VI (n=6). (B) In vitro ISO (I) (closed bars) stimulated cardiac adenylyl cyclase activity compared to vehicle (V) (open bars) in the Wt and TNFα-Tg mice of 6 or 20 weeks (n=6), *p< 0.005 versus respective I Wt samples (6 or 20 weeks). (C) βAR density on the plasma membranes isolated from the hearts of Wt and TNFα-Tg mice (n=6) of 6 or 20 weeks, *p< 0.001 versus 20 weeks Wt. (D) Plasma epinephrine (left panel) and norepinephrine (right panel) levels in Wt and TNFα-Tg mice at 6 weeks (n=6).