The effect of sulfhydryl reagents on the heart rate and coronary flow of the isolated perfused guinea-pig heart.

The action of a number of compounds able to react with thiols was tested on guinea-pig hearts perfused at constant pressure. The SH reagents used were NaNO2, oxidized glutathione, cystamine, diamide, 1,5-difluoro-2,4-dinitrobenzene, nitroglycerol, sodium nitroferricyanide and HgCl2. 6,6'-Dithiodinicotinic acid, an SH reagent that does not penetrate the cell, produced no effect. All the other SH reagents produced an increase in coronary flow. All except oxidized glutathione and nitroglycerol increased the heart rate. The increase in heart rate and oxygen consumption could be completely blocked by dichloroisoproterenol; the increase in coronary flow was not affected. Difluorodinitrobenzene, diamide, cystamine and NaNO2 significantly decreased the acid-soluble thiol content of the heart. For these compounds, there was a significant correlation between the decrease in coronary flow and the decrease in thiols. We conclude that in the isolated heart, most SH reagents, if used at the appropriate concentration, will increase the heart rate, probably by relaasing catecholamines. They will also decrease the coronary resistance, probably by a direct effect on the coronary vessels.