Figure 4.

Effect of transcription and translation inhibition on [Na⁺]i-dependent Na,K-ATPase cell surface expression in mpkCCD_cl4 cells. Confluent mpkCCDcl4 cells grown on polycarbonate filters were first preincubated in the presence of 15 mM or 135 mM Na⁺ without (–) or with (+)5 μM actinomycin D (Act; A and C) or 20 μM cycloheximide (Cyc; B and D) for 30 min at 37°C. After permeabilization by 1 μg/ml amphotericin B cells were incubated for 1 h at 37°C. Cell surface Na,K-ATPase was detected as described in the legend of Figure 2. (A and B) Representative immunoblots showing Na,K-ATPase cell surface expression. (C and D) Bars represent densitometric values expressed as the percentage of the optical density value measured in the presence of 15 mM Na⁺. Results are means ± SE from six independent experiments. *p < 0.05 vs. 15 mM Na⁺ values.