Abstract
We studied the effects of adenosine on injury caused by hypoxia and reoxygenation in LLC-PK1 cells. Lactate dehydrogenase and γ-glutamyltranspeptidase were released from cells exposed to hypoxia for 6 hr and then reoxygenation for 1 hr. The addition of adenosine at 100 μM to the medium before hypoxia began significantly decreased enzyme leakage into medium during both hypoxia and reoxygenation. The adenosine A1-receptor agonist, R(-)-N6-(2-phenylisopropyl)adenosine (R-PIA), at the concentration of 100 μM, did not affect enzyme release, but the adenosine A2-receptor agonist 2-p-[2-carboxyethyl]phenethyl-amino-5'-N-ethylcarboxamido-adenosine hydrochloride (CGS 21680) at the concentration of 100 nM, suppressed the injury caused by hypoxia and reoxygenation. There were decreases in cAMP contents and ATP levels in LLC-PK1 cells injured by hypoxia and reoxygenation. Adenosine (100 μM) restored ATP levels in the cells during reoxygenation. With adenosine, the intracellular cAMP level was increased prominently during reoxygenation. These results suggest that adenosine protects LLC-PK1 cells from injury caused by hypoxia and reoxygenation by increasing the intracellular cAMP level via adenosine A2 receptor.
