Impaired Cardiac cAMP-specific PDE4, β1-AR, and NE in an Ischemia-Reperfusion Rat Model

Abstract

Ischemic injury in the heart is followed by an increase in SNS activity and the higher this activity, the poorer patient outcomes. An index of SNS activity in models of ischemia can be achieved by measuring NE, β-AR, and perhaps indirectly PDE4 to give an intracellular aspect on SNS signaling. A 20 minute ischemia-reperfusion was induced in a rat model with physiological measurements at 2-5 weeks post IR. At 3 weeks post IR, rats displayed increased PDE4 expression, decreased β 1-AR expression, increased plasma NE, decreased tissue NE storage, increased Doppler E/A ratio and unchanged LV ejection fraction. PET analysis with FDG revealed no infarct at 2 weeks, while analysis with [13N]NH3 displayed no resting flow defect but revealed trends in flow reserve impairment as early as 2.5 weeks with recovery at 5 weeks post-surgery. Applications of this model could be non-invasive imaging of PDE4 with (R)-[11C]Rolipram PET at early time points for development towards prognostic and therapy guidance in humans.