Fig. 7. Effect of luminal L-histidine (L-His; 20 µmol l^–1) and both Cu⁺ and Cu²⁺ (50 µmol l^–1) on the kinetics of transmural transport of ⁶⁵Zn²⁺ (150–1000 µmol l^–1) measured over 30 min time intervals at each luminal ⁶⁵Zn²⁺ concentration. Unidirectional fluxes were calculated from regression slopes determined over this time interval for each ⁶⁵Zn²⁺ concentration. Values displayed are means ± S.E.M. of 3 replicates per concentration.