Table 1.

Composition of solutions used in the experiments

	Hepes buffers				NH4+ Hepes	HCO3− buffers
	Normal	Na+ free	Cl− free	NaCl free	Normal	Normal	Na+ free	Cl− free	NaCl free
NaCl	127	—	—	—	107	102	—	—
NaHCO3	—	—	—	—	—	25	—	25
KCl	4	2.9	—	—	4	4	2.9	—
MgSO4	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6
CaCl2	0.3	0.3	—	—	0.3	0.3	0.3	—
Na2HPO4	1.1	0	1.1	—	1.1	1.1	—	1.1
KH2PO4	0.6	1.7	0.6	1.7	0.6	0.6	1.7	0.6	1.7
Hepes	10	10	10	10	10	10	10	10	10
Glucose	6	6	6	6	6	6	6	6	6
NaOH	—	—	—	—	—	5	—	—
NMDG	—	132	0	132	—	—	132	—	132
Na-gluconate	—	—	127	—	—	—	—	102
K-gluconate	—	—	4	2.9	—	—	—	4	2.9
Ca-gluconate	—	—	0.3	0.3	—	—	—	0.3	0.3
Gluconolactone	—	—	—	127	—	—	—	—	104
NH4Cl	—	—	—	—	20	—	—	—

All values are stated in mm. Solutions were adjusted to pH 7.4 at 37°C using either HCl, NaOH or in the case of NaCl free solutions, Tris (tris hydroxymethylaminomethane). Buffers containing added HCO₃⁻ were bubbled with 5% CO₂−95% O₂ until the pH was stable.