Figure 5. Model for the interaction between NaCl- and H₂O₂-induced [Ca²⁺]_i increases.

A Ca²⁺ channel activated by NaCl (NaC) results in localized [Ca²⁺]_i increases, called NaC-related [Ca²⁺]_i microdomain (^NaC[Ca²⁺]_i). ^NaC[Ca²⁺]_i feedback inhibits the activity of NaC. HpC, a Ca²⁺ channel activated by hydrogen peroxide, leads to localized [Ca²⁺]_i increases, called ^HpC[Ca²⁺]_i microdomain. ^HpC[Ca²⁺]_i also feedback inhibits HpC activity. The [Ca²⁺]_i mircodomain-mediated inhibition of Ca²⁺ channels is the major feedback inhibitory pathways (thick lines). In addition, both ^NaC[Ca²⁺]_i and ^HpC[Ca²⁺]_i might contribute to a global [Ca²⁺]_i increase, which further inhibits both NaC and HpC, serving as global feedback inhibitory pathways (thin lines). [Ca²⁺]_i is reset to the resting level by plasma membrane Ca²⁺ pumps.