“Increasing … of l‐histidine enhanced 65Zn flux into brain at [ Zn2+ ] values between 1 and 1,000 nM. The combined effect of [histidine] and [Zn2+] was best accounted for by a function of [ZnHis+], i.e., flux = 64.4 · [ZnHis+]/(390 + [ZnHis+]) + 0.00378 · [ZnHis+], with concentrations being nanomolar.”