Figure 2.

Effect of extracellular CaSR agonists on AQP2 expression. Confluent mpkCCD_cl4 cells grown on filters in culture medium containing baseline (1 mM) calcium were preincubated at 37°C with 10⁻⁹ M AVP for 24 h. Cells were then incubated in the continuous presence of AVP for another 24 h without (Ctl) or with increasing concentrations of neomycin (A and B) or gadolinium,¹ two cationic CaSR agonists. Total protein extracts (40 μg) were separated by 10% SDS-PAGE and AQP2 and the Na-K-ATPase α-subunit, used as a loading control, were detected by Western blotting. (A and C) Representative immunoblot is shown. (B and D) Densitometric quantification of AQP2 protein expressed as a percentage of optical density values measured in the absence of drug (100%). Bars are means ± SEM from four to six independent experiments. *P < 0.05.