Prostacyclin release in the coronary circulation during sustained stimulation in in vitro and in in vivo experimental systems

Prostacyclin release from rat isolated perfused hearts and from dog coronary circulation was studied by measuring immunoreactive 6-keto-PGF1 alpha (6-keto-PGF1a) in heart perfusate and in plasma obtained from the great cardiac vein respectively. Continuous infusion of arachidonic acid at constant concentration in isolated perfused hearts induced an increased prostacyclin release. This release showed a rapid peak within 10 min and a subsequent decrease. Low-flow ischemia induced an increased perfusate concentration of 6-keto-PGF1a but, considering the decreased flow, prostacyclin release was actually reduced. During the whole period of ischemia (60 min) prostacyclin release was constant. In open-chest anesthetized dogs 6-keto-PGF1a concentration in the great cardiac vein was increased after ligation of the left anterior descending coronary artery. A prolonged period of coronary occlusion (4.5 hours) resulted in a progressive rise of prostacyclin release. 6-keto-PGF1a determinations in the femoral vein and in the aorta did not show relevant variations during the observation period.