A 1 Adenosine Receptor Activation Promotes Angiogenesis and Release of VEGF From Monocytes

Adenosine is a proangiogenic purine nucleoside released from ischemic and hypoxic tissues. Of the 4 adenosine receptor (AR) subtypes (A 1 , A 2A , A 2B , and A 3 ), the A 2 and A 3 have been previously linked to the modulation of angiogenesis. We used the chicken chorioallantoic membrane (CAM) model to determine whether A 1 AR activation affects angiogenesis. We cloned and pharmacologically characterized chicken AR subtypes to evaluate the selectivity of various agonists and antagonists. Application of the A 1 AR-selective agonist N 6 -cyclopentyladenosine (CPA; 100 nmol/L) to the CAM resulted in a 40% increase in blood vessel number ( P