Long-term myocardial preservation: thromboxane production and coronary resistance

In a series of 18 experiments on long-term myocardial preservation we evaluated whether vasoactive substances like thromboxane and prostacyclin are associated with the secondary increase in coronary resistance during preservation perfusion of the canine heart. In a control group (n = 12) and in a group treated with a specific thromboxane synthetase inhibitor (OKY 1581) coronary resistance was measured at 10 and 30 min, and at 1, 4, and 24 hr. At the same time intervals thromboxane A2 and prostacyclin (PGI2) production were determined as TXB2 and 6-keto PGF1 alpha, respectively. After OKY 1581 treatment no increase in TXB2 occurred and no secondary increase in coronary resistance was observed, while in the control group both TXB2 levels and resistance increased (P less than 0.01); 6-keto PGF1 alpha levels showed the same increase in control and in treated hearts. From this study it is concluded that during 24-hr myocardial preservation the characteristic secondary increase in coronary resistance is related to thromboxane production in the heart and is prevented by inhibition of thromboxane synthetase.