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ATP‐induced calcium oscillations and change of P2Y subtypes with culture conditions in HeLa cells

ATP, UTP, ADP and UDP induced intracellular Ca2+ responses and oscillations in HeLa cells that sometimes lasted over 1 h. The response is due to the activation of P2Ys, G‐protein coupled ATP receptors, because the oscillations persisted for several minutes even in Ca2+‐free solution, and suramin and PPADS, antagonists of ATP receptors, partially inhibited the response. The potency of these nucleotides varied with the culture or cell conditions, i.e. UTP was generally most potent but in some cases UDP was more potent; responses to UDP were variable while those to ATP were constant. In addition, Ca2+ responses to ATP and UDP were additive. These findings suggested the existence of two or more subtypes of P2Ys in HeLa cells. RT‐PCR experiments revealed the existence of P2Y2, P2Y4 and P2Y6. Recovery from starvation (culture in FBS‐free medium overnight and re‐addition of FBS) increased the responses to UTP and UDP but not to ATP, suggesting that the number or activity of P2Y6 and/or P2Y4 receptors may increase with cell proliferation in HeLa cells. Copyright © 2002 John Wiley & Sons, Ltd.