Figure 11.

Digital high-speed microscopy of a Ca²⁺ wave induced by mechanical stimulation of a single cell in Cx26–GFP HeLa cells. (A) Ca²⁺ changes in two neighboring cells are analyzed in the vicinity of two gap junctions. The locations of the gap junctions are indicated by the arrows and are derived from B. The color scale was chosen to enhance the visualization of small [Ca²⁺]_i changes, and the numbers represent minimal, saturating, and maximal percentage changes. (B) The corresponding fluorescent Cx26–GFP image indicates the location of the two gap junctions and the location of the four analysis points (marked with +, area = 2.3 × 2.3 μm) that were used to follow changes in [Ca²⁺]_i shown in C. The superimposed white line indicates the location of the adjacent plasma membranes. (C) The time course of [Ca²⁺]_i changes, represented as percentage of relative change of fluo-3 fluorescence, on either side of the two gap junctions at locations 1–4 indicated in B. These traces indicate that the delay times at the site of the gap junctions are very small. The [Ca²⁺]_i increase on the distal side of the gap junction begins immediately as the [Ca²⁺]_i is elevated on the near side of the gap junction but takes several seconds to reach a maximal level.