Figure 4.

NO-induced desensitization of the cGMP response. (A) HEK-GC/PDE5 cells were incubated with either 0 μM (control) or 3 μM GSNO for 5 min, washed with buffer to remove NO, and further kept at 37°C. After 60 min, cells were restimulated with GSNO (100 μM), and cGMP levels were measured at the indicated time points; the resulting cGMP response was reduced compared with control. In each experiment, data were normalized to the maximal cGMP level measured under control conditions. (B) HEK-GC/PDE5 cells were incubated with or without 3 μM GSNO for 5 min, washed with buffer to remove NO, and further kept at 37°C for 60 min. PDE5 activity was determined in supernatant fractions before incubation (control), directly after incubation with 3 μM GSNO (5 min), and 60 min after removal of NO (60 min).