Table 1.
Experimental solutions in Ussing chamber experiments (all concentrations were indicated as mM)
| Component | KRB (124 Cl−) | 30 butyrate KRB | HEPES buffer | HCO3−-free butyrate |
| NaCl | 115 | 85 | 145 | 115 |
| Na-butyrate | – | 30 | – | 30 |
| NaHCO3 | 25 | 25 | – | – |
| Component | 30 formate KRB | 60 butyrate KRB | 10 butyrate KRB | 3 butyrate KRB |
| NaCl | 85 | 55 | 105 | 112 |
| Na-butyrate | – | 60 | 10 | 3 |
| Na-formate | 30 | – | – | – |
| NaHCO3 | 25 | 25 | 25 | 25 |
All solutions contained (in mM) KCl (5), MgCl2 (1), CaCl2 (1), HEPES (10), and D-glucose (10), adjusted to pH 7.4 with NaOH (approximately 5 mM for titration), and were continuously gassed with a mixture of 95% O2–5% CO2 (for KRB or other bicarbonate buffers similar to KRB) or 100% O2 (for HEPES buffer and bicarbonate-free HEPES buffer)