Objective: To investigate the effect of exogeneous ATP on proliferation of renal tubular epithelial cells (LLC-PK1) and its intracellular mechanisms.
Methods: DNA synthesis was measured by 3H-thymindine incorporation, and proliferation was assessed by cell counting. MAP kinase activity was detected by phosphorylate specific substrate MBP.
Results: Exogeneous ATP (1-1000 mumol/L) significantly increased 3H-TdR uptake in a concentration dependent manner. It also increased cells proliferation. 100 mumol/L ATP rapidly activated MAP kinase. The potency of LLC-PK1 proliferation stimulated by ATP was similar to the effect of polypeptide growth factor EGF. Adenosine was less stimulatory effective than ATP. NBTI (50 mumol/L), an inhibitor of memberous nucleotide transportor, did not reduce the effects of ATP or Ado on proliferation of these cells.
Conclusions: Extracellular ATP is a potent mitogen of LLC-PK1 cells, and may promote stimulatory effect of EGF in these cells. This mitogenic effect is unlikely induced by ATP entering cells, but may be mediated by purinergic receptors which activate signaling pathway through MAP kinase cascade.