Effect of low frequency electromagnetic fields on A 2A adenosine receptors in human neutrophils

The present study describes the effect of low frequency, low energy, pulsing electromagnetic fields (PEMFs) on A 2A adenosine receptors in human neutrophils. Saturation experiments performed using a high affinity adenosine antagonist [ 3 H]‐ZM 241385 revealed a single class of binding sites in control and in PEMF‐treated human neutrophils with similar affinity ( K D =1.05±0.10 and 1.08±0.12 n M , respectively). Furthermore, after 1 h of exposure to PEMFs the receptor density was statistically increased ( P <0.01) (B max =126±10 and 215±15 fmol mg −1 protein, respectively). The effect of PEMFs was specific to the A 2A adenosine receptors. This effect was also intensity, time and temperature dependent. In the adenylyl cyclase assays the A 2A receptor agonists, HE‐NECA and NECA, increased cyclic AMP accumulation in untreated human neutrophils with an EC 50 value of 43 (40 – 47) and 255 (228 – 284) n M , respectively. The capability of HE‐NECA and NECA to stimulate cyclic AMP levels in human neutrophils was increased ( P <0.01) after exposure to PEMFs with an EC 50 value of 10(8 – 13) and 61(52 – 71) n M , respectively. In the superoxide anion (O 2 − ) production assays HE‐NECA and NECA inhibited the generation of O 2 − in untreated human neutrophils, with an EC 50 value of 3.6(3.1 – 4.2) and of 23(20 – 27) n M , respectively. Moreover, in PEMF‐treated human neutrophils, the same compounds show an EC 50 value of 1.6(1.2 – 2.1) and of 6.0(4.7 – 7.5) n M respectively. These results indicate the presence of significant alterations in the expression and in the functionality of adenosine A 2A receptors in human neutrophils treated with PEMFs.British Journal of Pharmacology (2002) 136 , 57–66; doi: 10.1038/sj.bjp.0704695