Figure 7.
Role of calmodulin in the calcium-induced attenuation of AVP-dependent AQP2 expression. (A) Confluent mpkCCDcl4 cells grown on filters were preincubated for 24 h at 37°C with 10−9 M AVP. Cells were then incubated for another 24 h in the continuous presence of AVP and in the presence of 1 or 5 mM apical calcium with or without 10−5 M W7 or trifluoperazine, two unrelated calmodulin inhibitors. After RNA extraction, real-time PCR was performed as described in the Concise Methods section using primers against AQP2. Results are expressed as a percentage of control values determined after 24 h of incubation in the presence of 1 mM calcium and in the absence of drugs (100%). Bars are means ± SEM from five to eight independent experiments. *P < 0.05.