Fig. 1.

The influence of insulin on ouabain-sensitive Rb uptake and Na,K-ATPase activity. Upper part: Ouabain-sensitive Rb uptake measured in cells exposed for 5 min to insulin (10–500 nM) or vehicle (control) in Rb-containing Krebs solution. Half of the cells in each group also received ouabain (500 μM) and ouabain-sensitive Rb uptake was calculated as the difference between uptake in the presence and absence of ouabain. Lower part: Na,K-ATPase activity (ouabain-sensitive ATP hydrolysis rate) measured in homogenates prepared from cells previously exposed for 5 min, 30 min, or 3h to 100 nM insulin or vehicle (control) in Krebs solution. ATP hydrolysis in the treated and control groups was measured under identical conditions. The values are the mean ± SEM of results from four to six independent experiments. ***(p < 0001) indicates a significant difference from control.