Figure 6.

The immediate Ca²⁺_i response is increased in cells expressing functional Cx43 channels. (a) The number of cells responding within 3 min with a Ca²⁺_i increase due to SN treatment (10 μM) was significantly enhanced in Cx43- and Cx43NT-expressing HeLa cells compared with HeLa-CTL or HeLa-Cx43CT cells. The percentage of cells with a Ca²⁺_i increase from the total cell number is expressed as mean±S.E.M.; *P<0.05 versus CTL/Cx43CT, n≥8 in at least three different cell cultures. In another series of experiments (b), the Ca²⁺ increase induced by SN (10 μM) was blocked by preincubation (15 min) with xestospongin C (xesto, 40 μM). The percentage of cells with a Ca²⁺_i increase from the total cell number is expressed as mean±S.E.M.; *P<0.05, NG; n=8 in three different cell cultures. (c) Inhibition of IP₃-mediated Ca²⁺ release (by xesto, 40 μM) reduces significantly SN (10 μM, 5 h)-induced apoptosis of HeLa-Cx43 cells but does not affect Cx-deficient control cells. Apoptosis was determined by annexin V-FITC/PI labelling and fold increase of apoptotic cells is expressed as mean±S.E.M.; *P<0.05 versus corresponding untreated; ^#P<0.05 versus Cx43 SN; n=6 in three different cell cultures