Fig. 1.

Endogenous NPR-A is down-regulated by ANP in primary bAEC. Cells were incubated with 200 nm ANP for the indicated periods of time at 37 C. A, Membranes were prepared and assayed for hormone-dependent guanylyl cyclase activity and plotted as a function of time in the presence of ANP. The data are representative of at least three separate experiments. B, In a parallel experiment, NPR-A was immunoprecipitated, fractionated by SDS-PAGE, electroblotted, and detected by immunoblot. NPR-A isolated from 293T cells stably expressing NPR-A was used as a positive control. A synthetic NPR-A blocking peptide was used as a negative control to block NPR-A antibody/antigen binding. NPR-A protein levels from three independent immunoblots were quantitated, normalized, and presented in graphical form as mean ± sem or range, where n = 3 (0, 4, and 8 h), n = 2 (1 and 2 h), or n = 1 (20 h). Statistical significance was determined by a paired t test, where *, P < 0.05.