Characterization of adenosine A1 receptor in cultured myoblast C2C12 cells of mice

In an attempt to investigate the presence of adenosine A1 receptor in cell line, we used N6-cyclopentyladenosine (CPA), an agonist of adenosine A1 receptor, to incubate with C2C12 cells in vitro. CPA increased the uptake of radioactive glucose into C2C12 cells in a concentration-dependent manner and this action was abolished by the antagonists, both 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (1,3-dipropyl-8-cyclopentylxanthine) and 8-(p-sulfophenyl)theophylline (8-SPT), at concentrations sufficient to block adenosine A1 receptor. Northern blot analysis showed the expression of adenosine A1 receptor mRNA by C2C12 cells. Western blotting also indicated a positive correlation (r=0.99) of antibody recognized adenosine A1 receptor with membrane protein. The presence of adenosine A1 receptor in C2C12 cells can thus be considered. In the presence of U73312 (1-[6[[(17β)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione), the specific inhibitor of phospholipase C, glucose uptake stimulated by CPA into C2C12 cells was reduced concentration-dependently while it was not modified by U73343 (1-[6[[(17β)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5-pyrrolidinedione), the negative control of U73312. Moreover, chelerythrine and GF 109203X (3-[1-[3-(dimethylamino)propyl]-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione) also diminished the CPA-stimulated glucose uptake at concentrations sufficient to inhibit protein kinase C. The obtained data suggest that activation of adenosine A1 receptor in C2C12 cells may increase the glucose uptake via phospholipase C-protein kinase C pathway.