Age-associated reductions in cardiac β1- and β2-adrenergic responses without changes in inhibitory G proteins or receptor kinases - Rui-Ping Xiao; Eric D. Tomhave; Ding-Ji Wang; Xiangwu Ji; Marvin O. Boluyt; Heping Cheng; Edward G. Lakatta; Walter J. Koch (Journal of Clinical Investigation, 1998)