Interaction between plasma potassium and epinephrine in coronary thrombosis in dogs.

BACKGROUND Both plasma potassium ([K]) and epinephrine concentrations have been known to increase during exercise and decrease rapidly shortly after exercise; in addition, it is also known that exercise can promote coronary thrombosis in human and animal subjects. Many studies have shown that epinephrine has a stimulatory effect on coronary thrombosis; however, little information is available concerning the effect of raising plasma [K] on coronary thrombosis. The present study was designed to investigate the effect of raising plasma [K] and its interaction with epinephrine infusion on coronary thrombosis. METHODS AND RESULTS A canine model of coronary thrombosis was used, and the frequency of cyclic blood flow reductions (CFRs) resulting from thrombus formation in the circumflex artery was analyzed in the study. By acutely raising plasma [K] to approximately 6.0 mEq/L, the frequency of CFRs was reduced from 8.0 +/- 0.6 to 3.7 +/- 1.0 in 40 minutes (P < .01). Epinephrine infusion (0.5 microgram.kg-1 x min-1) stimulated the frequency of CFRs from 7.1 +/- 0.5 to 11.5 +/- 0.7 in 40 minutes (P < .01). However, if plasma [K] was raised to approximately 6.0 mEq/L while the epinephrine infusion was continued, the frequency fell from 11.5 +/- 0.7 to 7.7 +/- 1.1 in 40 minutes (P < .01). CONCLUSIONS The present study demonstrated that acutely raising plasma [K] inhibited coronary thrombosis in dogs and also blocked the potentiating effect of epinephrine on coronary thrombosis. These findings may suggest that raising plasma [K] exerts a protective effect against coronary thrombosis and that a rapid decrease in plasma [K], such as that occurring shortly after exercise, facilitates coronary artery thrombosis when the artery has a preexisting pathological condition.