Protective effect of Mercurascan after coronary artery ligation in the dog.

The protective effect of hydroxymercurifluorescein (Mercurascan, MSC) on the ischemic myocardium was evaluated in dogs. MSC was given 17 min after ligation of the descending branch of the left coronary artery in closed-chest animals. The favorable effect of this drug was confirmed (1) by an immediate decrease of ST-segment elevation in electrograms from epicardial electrodes, (2) by a reduced number of Q waves 24 h after the ligation, and (3) by the preservation of CPK activity in the sites with moderate early ST-segment elevations. Microscopic examination also confirmed this. We conclude that MSC given shortly after coronary artery occlusion in dogs protects some cells in the border zone of ischemic focus from the development of necrosis. The membrane stabilizing effect or neutralization of proteolytic enzymes are the suggested explanations for the mechanism of MSC action.