Fig. 4. Effects of Na⁺-free medium or phloridzin (1 mmol l^-1) on 2-deoxyglucose (2-DG) uptake in cod (Gadus morhua) ventricle strips. After dissection, strips were incubated for 60 min in either regular medium (basal condition), Na⁺-free medium containing equimolar choline, or regular medium containing 1 mmol l^-1 phloridzin. All media were supplemented with 5 mmol l^-1 glucose, 35 mmol l^-1 mannitol and 0.1% bovine serum albumin (BSA). Ventricle strips were rinsed in glucose-free medium and then assayed for glucose uptake activity in the presence of 1 mmol l^-1 2-deoxy-D-[³H(G)]glucose. Values are means ± S.E.M. for six strips per bar. ^*P<0.01 versus basal condition.