VASCULAR TONE AND CONTRACTILITY DURING EXPOSURE TO CARDIOPLEGIA AND HYPERKALEMIC SOLUTIONS

Hyperkalemic cardioplegic solutions have been widely used for myocardi al protection. A commonly accepted concept is that cardioplegic soluti ons may evoke vasospasm due to the high potassium (K+) concentration i n the solutions. However, little has been known about coronary vascula r tone and contractility during ischemia and reperfusion. The present study was designed to test the hypothesis that hyperkalemic cardiopleg ic solutions may increase the vascular tone during exposure and increa se the contractility during reperfusion. Porcine coronary artery (PCA) and neonatal rabbit aortic (RAG) rings were set up in organ baths und er a physiologic pressure. In addition, the effect of reexposure to K on contractility was studied in-the human internal mammary artery (HI MA). The solutions were continuously aerated with 95% O-2 and 5% CO2 t o exclude the effects of ischemia and hypoxia. The effect of Krebs con taining 5.9 or 50 mM K+, or St. Thomas' cardioplegic solution No. 2 (S T) containing 16 or 50 mM K+ on vascular tone for four hours was exami ned. In other groups, after two-hour-incubation, the rings (n = 5 in P CA and n = 6 in RAO in each subgroup) were washed and cumulative conce ntration-contraction curves were established.