Figure 8.

Local photolysis of caged IP₃ triggered [Ca²⁺]_c increases, which propagate to neighboring cells. A) In a field of endothelial cells, locally photolyzed caged IP₃ in a single endothelial cell (i, yellow box) increased [Ca²⁺]_c in the activated cell (ii, green; iv, red) and a smaller response in an adjacent cell (iv, blue). The time course of the [Ca²⁺]_c changes, from the cells indicated by the regions of interest (iii), are shown in the line trace (iv). Immediately after photolysis (iv, ↑), a Ca²⁺ rise occurred in the activated cell, and a subsequent rise occurred in an adjacent cell some 20 s later. The Ca²⁺ changes in ii show all Ca²⁺ activity (i.e., each cell that responds is shown irrespective of time of response). B) IP₃ photoreleased simultaneously in 2 adjacent cells (i, yellow box) evoked a Ca²⁺ rise in each of the activated cells (ii, green; iv, red and blue lines) and Ca²⁺ rise in a neighboring cell (green) some 20 s later. The time course of the [Ca²⁺]_c changes, from the cells indicated by the regions of interest (iii), are shown in the line trace (iv). C) Photolyzed caged IP₃ in 4 cells simultaneously (i, yellow box) evoked a local Ca²⁺ increase, which rapidly propagated to a substantial number (∼18) of neighboring cells (ii–iv). The Ca²⁺ changes extended several cell lengths from the photolysis site (i, ii). The time course of the [Ca²⁺]_c changes, from the cells indicated by the regions of interest (iii), are shown in the line trace (iv). Scale bars, 50 µm.