Sympathetically induced myocardial ischaemia causes the heart to release plasma kinin

A recently developed highly sensitive radioimmunoassay method for detecting plasma kinin was used to re-evaluate the results of previous studies, in which plasma kinin had been measured with a bioassay method. To clarify the mechanism of plasma kinin release in global myocardial ischaemia the left main coronary artery was cannulated using a Griggs type autoperfusing cannula after pentobarbital anaesthesia in open chest dogs. The animals were divided into a non-coronary constricted group (n = 4) and a moderately coronary constricted group (n = 7). Cardiac sympathetic nerve stimulation (10 V, 4 Hz, 2 ms duration) was given to both groups. Haemodynamic recordings and blood samples were taken before and after coronary constriction as well as after sympathetic nerve stimulation. The arterial and coronary sinus plasma kinin concentrations were determined with the new radioimmunoassay method. After sympathetic nerve stimulation apparent myocardial ischaemia occurred and the plasma kinin concentration in coronary sinus blood increased significantly in the constricted group. In the non-constricted group, however, myocardial ischaemia did not appear and no significant change in coronary sinus plasma kinin concentrations was seen. These findings show that there was a pronounced release of plasma kinin from the heart when apparent myocardial ischaemia occurred.