Prostacyclin (PGI2) decreases the cyclic AMP level in coronary arteries.

The effects of prostacyclin (PGI2) on vascular tension and cAMP content were measured in isolated bovine coronary artery strips. 3 nM PGI2 did not alter the tension but diminished the cAMP content by 56% of the control level (P less than 0.005). 30 and 300 nM PGI2 diminished the tension and further reduced the cAMP content, which amounted to only 5% of the control at 300 nM PGI2. These results are in contrast to the increase in cAMP level by PGI2 in blood platelets and might indicate a different mechanism of action of PGI2 in platelets and vascular tissue.