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Ischemia aggravating effects of platelet-activating factor in acute myocardial ischemia
Insights
Platelet-activating factor (PAF) worsens myocardial ischemia in cats by increasing cell damage, potentially through thromboxane A2 release. Inhibiting thromboxane A2 synthesis reduces this damage, suggesting PAF
Area of Science:
- Cardiovascular Research
- Myocardial Ischemia Pathophysiology
Background:
- Platelet-activating factor (PAF) is implicated in inflammatory and cardiovascular responses.
- The role of PAF in acute myocardial ischemia requires further elucidation.
Purpose of the Study:
- To investigate the effect of PAF on myocardial ischemia in an acute setting.
- To determine if PAF exacerbates ischemic myocardial injury and if thromboxane A2 mediates this effect.
Main Methods:
- Anesthetized, open-chest cats underwent coronary artery ligation to induce myocardial ischemia.
- Platelet-activating factor (PAF) was infused at a specific dose before or after ischemia induction.
- Plasma creatine phosphokinase (CK) activity and myocardial CK content were measured.
- A thromboxane A2 synthetase inhibitor (CGS-13080) was used in some treatment groups.
Main Results:
- PAF infusion alone decreased blood pressure but did not affect heart rate or cell integrity markers.
- PAF administration post-coronary ligation significantly increased plasma CK activity and reduced myocardial CK content in the ischemic region.
- Treatment with CGS-13080 attenuated the PAF-induced increase in ischemic cellular damage.
Conclusions:
- Hypoxia-generated PAF may contribute to the aggravation of myocardial ischemia.
- PAF appears to exacerbate ischemic injury, partly via the release of thromboxane A2.
- Targeting thromboxane A2 synthesis may offer a therapeutic strategy against PAF-mediated myocardial damage.
Abstract:
The effect of platelet-activating factor (PAF) was studied during the acute phase of myocardial ischemia in cats. PAF infusion (0.75 micrograms/kg/h for 4.5h) in anesthetized, open-chest cat decreased arterial blood pressure, but did not influence heart rate or biochemical indices of cell integrity. The same dose of PAF, however, started 30 min after coronary ligation, resulted in a significantly higher elevation of plasma creatine phosphokinase (CK) activity and a reduced CK content in the region of the ischemic myocardium. Treatment with the thromboxane A2 synthetase inhibitor, CGS-13080, significantly attenuated the PAF-aggravated ischemic cellular damage. These experiments suggest that hypoxia-generated PAF may contribute to the aggravation of myocardial ischemia, part of which appears to be due to PAF-induced release of thromboxane A2.