Objective: A number of K⁺ channels are strictly regulated by small, fast changes in cell volume. The mechanisms underlying cell volume sensitivity are not known. A frequently stated hypothesis indicates that cell volume sensitivity is mediated by membrane stretch. In a recent study we presented evidence against this assumption by showing that the highly volume sensitive KCNQ1 channel is not affected by membrane stretch. Alternatively, volume-activation of ion channels could be mediated by an autocrine mechanism in which ATP released from the cells in response to volume changes activates signaling pathways that subsequently lead to ion channel stimulation. Our aim was to investigate whether volume sensitivity of KCNQ1 is dependent on ATP release. Methods: KCNQ1 K⁺ channels were co-expressed with AQP1 in Xenopus laevis oocytes and then subjected to volume changes by exposure to hypo- or hypertonic media with and without application of the ATP/ADP hydrolyzing enzyme apyrase. Currents were measured by TEVC. ATP release was measured by a luciferin-luciferase assay in non-injected and AQP1 injected oocytes before and after swelling. Results: In electrophysiological experiments it was shown that apyrase (7 U/ml) decreased all currents by about 50%. When oocytes were swelled by exposure to hypotonic medium, the relative increase in current was not affected by apyrase. Luminescence assay showed that there was a slight increase in ATP release in response to mechanical and hypotonic stimulus. However, cell volume response per se did not seem to induce higher release of ATP. Conclusion: The presence of AQP1, and consequently the faster volume change to hypotonic stress, does not induce higher ATP release to surrounding medium in our assay settings. Based on our data to date, we postulate that release of ATP is not involved in the regulation of KCNQ1 channels during cell volume changes.