The PS product for K+ was [419] 11.3 µL min−1 g−1. This larger value is based on fluxes that were somewhat smaller than those for Na+ but at substantially smaller concentrations, e.g. 4 mM rather than 140 mM. Unlike those for Na+, the fluxes for K+ can be substantially reduced by inhibitors of transporters known to be present in the endothelial cells (reviewed in [4]).