Relaxation by prostacyclin (PGI2) and 7-oxo-PGI2 of isolated cerebral, coronary and mesenteric arteries.

The relaxant effects of prostacyclin (PGI2) and its stable 7-oxo-analogue, a product of Chinoin Pharmaceutical Works, were compared on isolated canine cerebral, bovine coronary, rabbit coeliac and human mesenteric arterial strips. The resting tone of the coronary, cerebral and human mesenteric arteries as well as the stimulation- or noradrenaline-evoked tone of coeliac vessels were reduced by both prostanoids. The relaxant action of 7-oxo-PGI2 was slow in onset and lasted until it was washed out. The IC50 values were 4 to 40 X 10(-9) mol/l for PGI2 and 1 to 6 X 10(-7) mol/L for 7-oxo-PGI2. Compared to PGI2, 7-oxo-PGI2 was more potent in relaxing coronary arteries than the other vessels studied. Isolated tracheae from guinea-pigs were contracted by PGI2 while relaxed by 7-oxo-PGI2.