Figure 6. Osmotic response of TRPV1 is potentiated under acidic conditions.
(A) Representative single cell traces of the fluorescence ratio during the perfusion of solutions with the respective osmolality at 36°C. The top line indicates the timing of the change from the control solution (pH 7.4, 300 mOsm; gray) to the acidic solution (pH 6.6) with the respective osmolality (black). (B) Summary of the change in the fluorescence ratio. Data are differences between fluorescence ratios 2 min before and 4 min after the change of the solution. The osmotic response of the [Ca2+]i in HEK293-TRPV1 cells (filled circles) was enhanced by acidification over the entire osmolality range (compare with filled triangles). This was evident especially in the hypertonic range. Values are the mean ± SEM; when the SEM value was less than 0.07, the error bar is hidden behind the symbol. HEK293-TRPV1, pH 7.4: n = 138 (250 mOsm), n = 151 (300 mOsm), n = 214 (350 mOsm). HEK293-TRPV1, pH 6.6: n = 151 (250 mOsm), n = 144 (300 mOsm), n = 251 (350 mOsm). HEK293, pH 6.6: n = 129 (250 mOsm), n = 131 (300 mOsm), n = 156 (350 mOsm).