Table 1.
Fast-acting signaling agents H2O2and Ca2+occur at nanomolar concentration. Proton concentration [H+] is at similar concentration. Columns are in nanomolar [nanomol/L] and as p = –log10 [mol/L], to illustrate the similar physiological ranges for H2O2, Ca2+ and H+. Numbers refer to generic resting cells, ranges not shown; exact quantification in subcellular organelles is yet to be obtained.
| H2O2 |
Ca2+ |
H+ |
||||
|---|---|---|---|---|---|---|
| nM | (pH2O2) | nM | (pCa) | nM | (pH) | |
| ‘Overall cellular’a | 10 | (8) [128,129] | 100 | (7) | 100 | (7) |
| Cytosol | 0.1 | (10) [53] | <100 | (>7) | 100 | (7.0) |
| Mitochondrial matrix | 4 | (8.4) [54] | <100 | (>7) | 40 | (7.4) |
| Endoplasmic reticulum | 700 | (6.2) [52] | 500,000 | (3.3) | 60 | (7.2) |
| Golgi | 300 | (6.5) [130] | 300,000 | (3.5) | 400 | (6.4) |
| Peroxisome | ? | <100 | (>7) | 7 | (8.2) [69] | |
| Lysosome | ? | 300,000 | (3.5) [131] | 3200 | (5.5) | |
a
For rough orientation only: considerable subcellular variation; Ca2+ in various spaces was arbitrarily set to <100 nM.