. (**A**) Schematic representation of the 0-D spherical geometry representing a solid tumor with a hypoxic core. Results of modelling shown as radial concentration gradients at the steady-state for (**B**) lactate, (**C**) HCO~0~^−^ and (**D**) pH in the intracellular space. Arrows indicate direction of diffusive flux. For comparison, dashed lines show results with no junctional coupling, from [Figure 0](#cancers-00-00000-f000){ref-type="fig"}. 