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Effect of intact endothelium against platelet-induced coronary artery spasm in isolated rabbit hearts
Insights
Collagen-activated platelets cause coronary artery spasm in denuded arteries, but not intact ones. This highlights the protective role of intact endothelium against platelet-induced vasoconstriction.
Area of Science:
- Cardiovascular Physiology
- Platelet Biology
- Endothelial Function
Background:
- Platelets play a crucial role in hemostasis and thrombosis.
- Endothelial cells lining blood vessels provide a barrier and regulate vascular tone.
- Coronary artery spasm is a significant cause of myocardial ischemia.
Purpose of the Study:
- To investigate the effect of collagen-activated rabbit platelets on coronary arteries with and without intact endothelium.
- To determine the role of the endothelium in mediating or preventing platelet-induced coronary vasoconstriction.
Main Methods:
- Utilized a supported rabbit heart preparation perfused with perfluorocarbon (FC-43).
- Assessed coronary artery diameter using gated color arteriography.
- Induced endothelial denudation by scraping the arterial lumen.
- Injected washed platelets, with and without collagen activation, into coronary arteries.
Main Results:
- Unactivated platelets did not cause coronary artery constriction.
- Collagen-activated platelets induced significant vasoconstriction and occlusion in denuded coronary arteries (10/14 cases).
- No vasoconstriction was observed in coronary arteries with intact endothelium.
- Total coronary vascular resistance increased in hearts with induced spasm.
Conclusions:
- Endothelial lesions contribute to coronary artery spasm.
- Intact endothelial cells exert a protective function against vasoconstrictor substances released by aggregating platelets.
- Platelet activation and aggregation are implicated in the pathogenesis of coronary artery spasm, particularly when the endothelium is compromised.
Abstract:
Effects of collagen-activated washed rabbit platelets on coronary arteries with and without intact endothelium were studied in a supported rabbit heart preparation using a perfluorocarbon (FC-43) as perfusate. The vascular diameter of obtuse marginal coronary arteries was determined by means of gated color arteriography (injection of patent blue dye). Endothelial denudation of the obtuse marginal artery was accomplished by scraping the lumen with a roughened plastic tubing. Injection of washed platelets (10 ml with about 500,000 platelets/microliters) not treated with collagen failed to constrict coronary arteries either with intact or denuded endothelium. In contrast, injection of platelet suspension immediately after activation with collagen caused vasoconstriction of denuded obtuse marginal coronary arteries in 10 of 14 cases. In 6 preparations occlusion was complete, lasting up to 16 minutes. In arteries with intact endothelium, no coronary vasoconstriction occurred. In hearts with coronary artery spasm, total coronary vascular resistance increased significantly. This study furnishes additional evidence that endothelial lesions are a contributory factor for large coronary artery spasm and that endothelial cells possess a protective function against vasoconstrictor substances released from aggregating platelets.