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Abstract-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 (PϽ0.01), which was blocked by the A 1 AR-selective antagonist C 8 -(N-methylisopropyl)-amino-N 6 -(5Ј-endohydroxy)-endonorbornan-2-yl-9-methyladenine (WRC-0571; 1 mol/L). Selective A 2A AR agonists did not stimulate angiogenesis in the CAM. In an ex vivo rat aortic ring model of angiogenesis that includes cocultured endothelial cells, fibroblasts, and smooth muscle cells, 50 nmol/L CPA did not directly stimulate capillary formation; however, medium from human mononuclear cells pretreated with CPA, but not vehicle, increased capillary formation by 48% (PϽ0.05). This effect was blocked by WRC-0571 (1.5 mol/L) or anti-VEGF antibody (1 g/mL). CPA (5 nmol/L) stimulated a 1.7-fold increase in VEGF release from the mononuclear cells. This is the first study to show that A 1 AR activation induces angiogenesis. Stimulation of A 2 ARs on endothelial cells results in proliferation and tube formation, and A 2 and A 3 ARs on inflammatory cells modulate release of angiogenic factors. We conclude that adenosine promotes a coordinated angiogenic response through its interactions with multiple receptors on multiple cell types. (Circ Res.

Dunn MJ, Shattock MJ. Characterization of the phospholemman knockout mouse heart: depressed left ventricular function with increased Na-K-ATPase activity. Am J Physiol Heart Circ Physiol 294: H613-H621, 2008. First published December 7, 2007 doi:10.1152/ajpheart.01332.2007, abundantly expressed in the heart, is the primary cardiac sarcolemmal substrate for PKA and PKC. Evidence supports the hypothesis that PLM is part of the cardiac Na-K pump complex and provides the link between kinase activity and pump modulation. PLM has also been proposed to modulate Na/Ca exchanger activity and may be involved in cell volume regulation. This study characterized the phenotype of the PLM knockout (KO) mouse heart to further our understanding of PLM function in the heart. PLM KO mice were bred on a congenic C57/BL6 background. In vivo conductance catheter measurements exhibited a mildly depressed cardiac contractile function in PLM KO mice, which was exacerbated when hearts were isolated and Langendorff perfused. There were no significant differences in action potential morphology in paced Langendorff-perfused hearts. Depressed contractile function was associated with a mild cardiac hypertrophy in PLM KO mice. Biochemical analysis of crude ventricular homogenates showed a significant increase in Na-K-ATPase activity in PLM KO hearts compared with wild-type controls. SDS-PAGE and Western blot analysis of ventricular homogenates revealed small, nonsignificant changes in Na-K-ATPase subunit expression, with two-dimensional gel (isoelectric focusing, SDS-PAGE) analysis revealing minimal changes in ventricular protein expression, indicating that deletion of PLM was the primary reason for the observed PLM KO phenotype. These studies demonstrate that PLM plays an important role in the contractile function of the normoxic mouse heart. Data are consistent with the hypothesis that PLM modulates Na-K-ATPase activity, indirectly affecting intracellular Ca and hence contractile function. FXYD1; contractile function; intracellular sodium regulation IN EXCITABLE TISSUES, the activity of the plasma membrane Na-K-ATPase is vital for the maintenance of normal electrical activity, ionic homeostasis, cell volume control, and substrate and amino acid transport and for setting cellular Ca load and hence contractility. Interventions that influence Na-K-ATPase activity and/or the transmembrane Na gradient can therefore profoundly affect myocardial function. In essence, the Na-KATPase not only influences a wide range of transmembrane transport processes but also indirectly controls myocardial contractility.It has recently been recognized that the FXYD family of small single transmembrane-spanning proteins are tissue-specific regulators of the Na-K-ATPase (3-5, 28). Phospholemman (PLM, FXYD1) is expressed in excitable tissues and is unique among the FXYD proteins in that it contains a cytoplasmic region with consensus phosphorylation sites for kinases that include PKC and PKA (21, 30). In fact, PLM was originally identified as the primary sarcolemmal ...