Effect of low frequency electromagnetic fields on A2A adenosine receptors in human neutrophils

1 The present study describes the effect of low frequency, low energy, pulsing electromagnetic fields (PEMFs) on A(2A) adenosine receptors in human neutrophils. 2 Saturation experiments performed using a high affinity adenosine antagonist [H-3]-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 nM, 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). 3 The effect of PEMFs was specific to the A(2A) adenosine receptors. This effect was also intensity, time and temperature dependent. 4 In the adenylyl cyclase assays the A(2A) receptor agonists, HE-NECA and NECA, increased cyclic AMP accumulation in untreated human neutrophils with an EC50 value of 43 (40-47) and 255 (228-284) nM. 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 EC50 value of 10(8-13) and 61(52-71) nM, respectively. 5 In the superoxide anion (O-2(-)) production assays HE-NECA and NECA inhibited the generation of O-2(-) in untreated human neutrophils, with an EC50 value of 3.6(3.1-4.2) and of 23(20-27) nM, respectively. Moreover, in PEMF-treated human neutrophils, the same compounds show an EC50 value of 1.6(1.2-2.1) and of 6.0(4.7-7.5) nM respectively. 6 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.