Stimulation of cyclic GMP formation in smooth muscle cells by atriopeptin II

Addition of synthesized atriopeptin II (AP-2), a 23 amino acid peptide of rat atria, to rat thoracic aorta smooth muscle cells results in the stimulation of cyclic GMP production by the cells. The EC50 for the effect is 81 nM and a 7 fold increase occurs at 10 microM AP-2. Cyclic GMP levels increased within 15 seconds after the addition of AP-2 and were maximal at 5 minutes. Cyclic GMP levels in primary rabbit kidney cells were increased 15 fold by 10 microM AP-2. However, no increase in cyclic GMP was detected in WI-38 fibroblast cells after the addition of 10 microM AP-2. Cyclic AMP levels were not affected by AP-2 in any of these cell systems. The effect upon cyclic GMP accumulation was specific for AP-2; none of the other compounds or peptides tested affected cyclic GMP levels.