the comparison of cell sodium activity and cell ph ( yoshitomi and fromter [ 17 ] ) demonstrates that the electrochemical potential difference of na+ is greater than that of h+ , as required for the operation of na+/h+ counter transport in the brushborder membrane but that bicarbonate efflux via the sodium bicarbonate cotransport system at the peritubular cell membrane requires a hco3- to na+ stoichiometry of greater than 2.0 or the involvement of other ions at least under free-flow conditions .
C0007634
cell
C0007603
cell membrane