Effect of hemin on cGMP levels in HN33 cells.

Cells were treated for the indicated times with 50 μM hemin, in the absence and presence of KT5823 (8 μM) or LY83583 (1 μM), and cGMP levels were measured as described in “Materials and methods.” Data are mean ± SEM from 4 experiments. *P < .05 compared with treatment for 2 hours with hemin alone (second bar from left); **P < .01 compared with control (unfilled bar).