FIGURE 2.

Albumin induces the expression of (Na⁺ + K⁺)-ATPase α1 subunits. A, LLC-PK1 cells were grown on coverslips, kept in medium depleted of serum in the absence (a–c) or in the presence of 0.01 mg/ml (d–f) or 20.0 mg/ml (g–i) albumin. After treatment, the cells were washed with PBS²⁺, and immunofluorescence was performed. The (Na⁺ + K⁺)-ATPase α1 subunits are shown in green. Blue (DAPI) represents the nucleus. Scale bar, 10 μm (n = 3). B–D, LLC-PK1 cells were kept overnight in medium depleted of serum in the absence or presence of 0.01 mg/ml albumin. Immunoblotting was performed for the (Na⁺ + K⁺)-ATPase α1 subunit in cell homogenate (B, n = 5), in the membrane fraction (C, n = 6), or on the cell surface of basolateral membrane (D, n = 4). Error bars, S.E. *, statistically significant in relation to the control (in the absence of albumin).