Aggregated platelets and occlusive platelet thrombi were found in small myocardial vessels of dogs on electron-microscope examination after prolonged infusion of norepinephrine. The etiology of the myocardial necrosis and fibrosis induced by catecholamines in experimental animals and seen in patients with pheochromocytoma and patients after norepinephrine treatment for shock may be related to this intravascular platelet-aggregating effect of catecholamines. The link between stress and acute myocardial infarction may be via catecholamine-induced intravascular platelet thrombosis. If the thrombogenic theory of atherosclerosis is valid, platelet aggregation induced by catecholamines may be the mechanism whereby arteriosclerotic heart disease is related to stress.
SUMMARYIntravascular aggregation of platelets similar to that found in dogs after norepinephrine infusion was demonstrated using the electron microscope in the hearts of 20 of 23 rats subjected to two forms of stress (immersion in hot water, 7 of 8 rats; repeated small electric shocks to the feet, 13 of 15 rats). Received January 9, 1973; revision accepted for publication March 5, 1973. 164 lodges in a coronary artery previously narrowed by atherosclerosis. To determine whether the catecholamines produced endogenously during stress are sufficient to cause intravascular platelet aggregation similar to that seen after exogenous infusion of norepinephrine,4 5 studies with rats stressed by immersion in ice water were conducted and similar platelet aggregates were noted on electron microscopic examination of the heart." It was not clear, however, what effect cold temperature per se had on the tendency for platelet aggregation to occur intravascularly in the heart. To further document that the intravascular platelet aggregates noted in the previous study were indeed due to the stress, 2 other forms of stress-immersion in hot water and repeated electrical shocks to the feet of rats-were studied and reported here. Electron microscopic findings in rats stressed in this way were similar to those found after cold stress, with intravascular platelet aggregates found in the small vessels of the heart.Material and Methods Thirty-seven white laboratory rats weighing 300-500 g were used for study.Eight rats were stressed by immersion in a tub that contained 4 to 5 inches of water kept at 500 by addition of small amounts of boiling water. The four to five inch water level was chosen to allow the rats to just touch bottom and keep their noses above the water. At the first sign of fatigue (inability to maintain head out of water), the rats were promptly removed from the water bath and killed with a blow on the head and removal of Circulation, Volume XLVIII,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.