Heparin treatment induces increases in cGMP concentration. Panel A: A7r5 cells were cultured in 150 mm dishes, starved as described in Methods and treated with 200 μg/ml heparin for indicated times. The cGMP concentrations were determined as described in the assay protocol and are reported as fold increases. The means (± SE) represent three independent experiments. Heparin increased cGMP after 5, 10 and 20 min (p<0.0051, 0.0011, and 0.0222, respectively). Panel B: A7r5 cells were cultured in 150 mm dishes and treated with heparin (200 μg/ml), 18H6 antibody (0.8 μg/ml) or ANP (100 nM) for 10 min. The data represent triplicate repeats. Values are reported as fold increases. Heparin treatment resulted in a statistically significant increase in cGMP (p < 0.0032).