Fig. 1. Profile of ⁶⁵Zn(II) activity obtained from the efferent cannula following perfusion of the intestine with 50 µmol l^–1 Zn(II) alone (control), or in solution with 100 mmol l^–1 L-cysteine or L-histidine. Values are means ± S.E.M. (N=4–6 for amino acid treatments, N=10 for control). Slope values (3.98 for L-cysteine, 3.71 for L-histidine, and 2.71 for Zn(II) alone) were calculated over the linear phase of outflow (approx. 20–50 min).