Table 1.

List of variables used in the mathematical model for simulating steady-state pH and lactate concentration under the various scenarios presented in Fig.s 2, 3 and 4

Parameter	Definition	Fig 2	Fig 3	Fig 4	Reference
r	Radius of cell	7 μm	7 μm	7 μm	[37]
R	Distance from capillary	(case 1) 0 μm (2–3) 150 μm	(case 1–2) 0 μm (3) 150 μm	150 μm	[38]
pHi0	Starting intracellular pH	7.3	7.3	7.3
pHec	Extracellular pH in capillary	7.4	7.4	7.4
β int	Intrinsic buffering capacity	15 mM/pH	15 mM/pH	15 mM/pH	[39]
β e	Extracellular buffering capacity	3 mM/pH	3 mM/pH	3 mM/pH	[40, 41]
D H	Interstitial H+ diffusion coefficient	12,000 μm2/s	12,000 μm2/s	12,000 μm2/s	[40, 41]
τ e	Tortuosity in extracellular space	0.5	0.5	0.5	[40, 41]
J CO2	CO2 production rate	0–15 mM/min	0	0	[42]
K CO2	CO2 dissociation constant	10–6.15 M	10–6.15 M	10–6.15 M
k h	Spontaneous CO2 hydration constant	0.16 s−1	0.16 s−1	0.16 s−1	[38, 40, 41]
CAe	Extracellular CA activity	(case 1–2) 1 (3) 1000	1000	1000	[38, 40, 41]
[CO2]ec	Extracellular CO2 concentration in capillary	1.2 mM	1.2 mM	1.2 mM
P CO2	CO2 membrane permeability	1000 μm2/s	1000 μm2/s	1000 μm2/s	[40]
D CO2	Interstitial CO2 diffusion coefficient	2400 μm2/s	2400 μm2/s	2400 μm2/s	[40]
D HCO3	Interstitial HCO3− diffusion coefficient	1800 μm2/s	1800 μm2/s	1800 μm2/s	[40]
J HLa	Lactic acid production rate	0	0–20 mM/min	0–20 mM/min	[43–48].
K HLa	Lactic acid dissociation constant	–	10–3.86 M	10–3.86 M
[HLa]ec	Extracellular lactic acid concentration in capillary	–	0 mM	0 mM
P HLa	Apparent lactic acid membrane permeability	–	(case 1) 10 μm/s (2–3) 1000 μm/s	1000 μm/s
D La	Interstitial lactate diffusion coefficient	–	1300 μm2/s	1300 μm2/s	[40]
D HLa	Interstitial lactic acid diffusion coefficient	–	1300 μm2/s	1300 μm2/s	[40]
V max	Maximum flux generated by active transporter	–	–	(case 1) 0 mM/min (2) 1 mM/min (3–4) 10 mM/min
K a	Apparent H+ binding constant of active transporter	–	–	(1–3) 10–7.0 M (4) 10–6.7 M	[31, 39]
n	Hill cooperativity of active transporter	–	–	2	[31, 39]
J loading	Regulated acid-loading flux			(case 1) 0 mM/min (2) 0.2 mM/min (3–4) 2 mM/min
pHsetpoint	Intracellular pH setpoint	–	–	(case 1–3) 7.3 (4) 7.0