Growth inhibitory effects of ATP and its derivatives on human fibroblasts immortalized with Co-60-gamma rays

In our previous study (Katayama B et al, Int J Mol Med 2: 603-606, 1998), c ell growth inhibition caused by ATP added to cultures was found to be great er in immortalized human fibroblasts than in the normal human fibroblasts. Since it has been reported that ATP affects cells via P2-purinergic recepto rs, growth inhibitory effects of ATP and its derivatives on immortalized hu man fibroblasts were investigated in the present study in order to learn wh at type of receptors are involved in ATP cytotoxicity. The ATP derivatives used in this study were: ATP, ADP, beta, gamma-methyleneadenosine 5'-tripho sphate (MeATP), 2' & 3'-o-(4-benzoylbenzoyl) adenosine, triethylammonium sa lt (BzATP), adenosine 5'-o-(3-thiotriphosphate) (ATP gamma S), 2-methylthio adenosine 5'-triphosphate (2-MeSATP) and UTP. The extent of cytotoxicity in duced by these drugs was found to be in the order of: ATP=ADP>ATP gamma S>M eATP=BzATP. On the other hand, neither 2-MeSATP nor UTP showed any cytotoxi city. These findings indicate that ATP may exert the cell growth inhibition by certain kinds of signal transduction via P2x or P2y purinergic receptor s which affect intrinsic channels/pores of cell membrane and/or G protein a ctivation. As a result, intracellular elevation in the concentrations of io ns such as calcium and potassium, membrane depolarization, loss of endogeno us ions/metabolites, and activation of inositol phospholipid-specific phosp holipase C may occur. Actually, a dihydropyridine calcium channel blocker, nifedipine, and an ATP-sensitive K+-channel blocker, glybenclamide, reduced the growth inhibitory effects of ATP on the cells to some extent. The grow th inhibition caused by ATP was not due to apoptosis or induction of a cycl in/CDK kinase inhibitor, P21.