Calcium mediates the inhibitory effect of the D4 receptor on AT1 receptor expression in WKY RPT cells.
A. Effect of D4 receptor agonist, PD168077 (10-6M/24hrs) and calcium channel blocker, nicardipine (10-6M/24hrs), on AT1 receptor protein expression in WKY RPT cells. The cells were incubated with the indicated reagents. Results are expressed as the ratio of AT1 receptor and α–actin densities (n = 6, *P<0.05 vs. others).
B. Effect of a D4 receptor agonist, PD168077 (10-6M/24hrs), on AT1 receptor expression in WKY RPT cells incubated in medium with or without calcium. Results are expressed as the ratio of AT1 receptor and α–actin densities (n = 5, *P<0.05 vs. others).