Fig. 10. Na⁺ (white bars) and K⁺ content (grey bars) content of intestinal cells exposed external [Cu] (Cu_o) ranging from 0 (no added Cu) to 800 µmol l^–1 for 15 min (A) in low external chloride (Cl^–_o=6.6 mmol l^–1, Cl^–_o replaced by sodium gluconate), (B) with 0.1 mmol l^–1 DIDS in normal saline, and (C) at low external pH (pH 5.5). Values are means ± S.E.M. of N=5–6 separate experiments using fresh cells from different individual fish. ^*Statistically significant difference from control with no added Cu within treatment and electrolyte (Kruskal–Wallis test, P<0.05).