Figure 2. Opening of stretch-activated channels causes only a global increase in [Ca²⁺]_i when the pipette solution at the extracellular surface of the channels is Ca²⁺ free (0 Ca²⁺, 0.2 mM BAPTA).

The results presented here are from the same type of experiment as in Fig. 1 except that Ca²⁺ was omitted from the pipette solution and 0.2 mM BAPTA was added to it. Note the reduction in the unitary current amplitude in the expanded current record (each ≈0.5 s in duration), indicative of membrane depolarization during continued membrane stretch. In the absence of Ca²⁺ in the pipette, stretch-activated unitary currents are larger (Kirber et al. 1988). The region near the centre of the cell where [Ca²⁺]_i appears to rise less during the stretch and where after cessation of stretch [Ca²⁺]_i remains slightly elevated is occupied by the nucleus. The colour bar provides a linear scale for [Ca²⁺]_i from 0 to 300 nM.