“In contrast, salicylate (another anion) and quinine (a cation) inhibited the uptake of allantoin only at concentrations which simultaneously increased the water content of the slices.”
“Salicylate (an anion) and quinine (a cation), in dosage which inhibited allantoin uptake, also inhibit the uptake of the para-aminohippuric acid (an anion) and tetraethylammonium bromide (a cation).”