Fig. 4.

CLA concentration dependence of unidirectional Na⁺ (○) and Rb⁺ (•) uptake in isotonic medium. To initiate flux, cells were transferred to ²²Na⁺- and ⁸⁶Rb⁺-containing medium at the CLA concentration indicated in the ordinate axis. Both Na⁺ and Rb⁺ unidirectional uptake rates were measured and expressed as mmol·kg dcs⁻¹·min⁻¹. The data were fit to a sigmoidal dose-response function by nonlinear regression to obtain values for the half-maximal stimulatory concentration (EC₅₀) of CLA for Na⁺ (dashed line) and K⁺ (solid line) flux. EC₅₀ values for CLA in this experiment were 42.3 nM for Na⁺ flux and 39.9 nM for K⁺ flux. Similar results were obtained in 3 experiments.