The pHi and the TMP of Human Red Blood Cells as a Function of the pHo , Chloride [Cl−]o , and Sucrose Concentration
| [Cl−]o (mmol/L) . | [Sucrose]o (mmol/L) . | pH0 . | pHi (theoretical) . | pHi (experimental) . | TMP [mV] (theoretical) . |
|---|---|---|---|---|---|
| 120 | 30 | 8.5 | 8.3 | ND | −12.1 |
| 120 | 30 | 7.4 | 7.4 | 7.2; 7.1 | −0.3 |
| 120 | 30 | 5.8 | 5.7 | 5.9; 5.9 | 7.2 |
| 5 | 280 | 7.4 | 8.1 | 7.7; 7.8 | 39.4 |
| 5 | 280 | 5.8 | 6.8 | 6.6; 6.6 | 52.4 |
| [Cl−]o (mmol/L) . | [Sucrose]o (mmol/L) . | pH0 . | pHi (theoretical) . | pHi (experimental) . | TMP [mV] (theoretical) . |
|---|---|---|---|---|---|
| 120 | 30 | 8.5 | 8.3 | ND | −12.1 |
| 120 | 30 | 7.4 | 7.4 | 7.2; 7.1 | −0.3 |
| 120 | 30 | 5.8 | 5.7 | 5.9; 5.9 | 7.2 |
| 5 | 280 | 7.4 | 8.1 | 7.7; 7.8 | 39.4 |
| 5 | 280 | 5.8 | 6.8 | 6.6; 6.6 | 52.4 |
pHi and TMP were calculated by a model44,46,47 (for details, see Brumen et al46 and Glaser44,45 ) assuming a time-independent equilibrium of water, chloride, and pH across the red blood cell. By taking into account (1) the condition of electroneutrality, (2) the pH dependence of the hemoglobin charge, (3) the activity coefficients, and (4) the equilibration of the osmotic pressure π (Δπ = πo − πi = 0), the intracellular and extracellular concentrations of Cl− and H+are given by the Nernst equation. For calculation, we have assumed an intracellular Na+-K+ concentration of 146 mmol/L cell water, a hemoglobin concentration of 7 mmol/L cell water at a relative volume of the erythrocyte 1,45,64 and a temperature of 4°C. According to the composition of the suspension media used, the glucose concentration of 5 mmol/L and an ionic strength of the buffer concentration 30 mmol/L were taken into account for calculations. It has been shown that the model provides a faithful description of the measured TMP and pHi .44 47 The experimentally determined intracellular pH is given (T = 4°C; 2 independent experiments).
Abbreviation: ND, not determined.