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Experimental study on microthrombi and myocardial injuries
Abstract:
The experiment was conducted with SD male rats. After they had been each given an intravenous injection of high molecular weight dextran (0.8 ml/100 g body wt) once a day for 4 days, they were brought under the observation of ECG and mesentery microcirculation. Microthrombi were found in the venules and capillaries of each rat of the experimental group, while in the microcirculation of the control group rats, no microthrombi were found. No changes were found in the ECGs of the rats (n = 6) in the control group after the injections, while the rats in the subject group all suffered a rise in the S-T segment of ECG, an indication of myocardial injuries. The rise was significantly in positive correlation to the increase in microthrombi in number (r = 0.944, P < 0.01). The erythrocytes of the rats in the subject group clustered to become rouleau-like, and platelets aggregated by tens and hundreds to form microthrombi. Their blood also showed a significant decrease in number of platelets. The degree of platelet aggregation and the scores of the rise on ECG were significantly in positive correlation as shown by the results: y = 20 + 94x, r = 0.94, P < 0.01. The plasma TXB2 of the subject group increased obviously but the change of 6-K-PGF1 alpha in the blood was not significant. The content of plasma TXB2 and the scores that indicated the rise in the S-T segment of the ECG showed significantly a positive correlation by the analysis of linear regression equation: y = 109.997 +/- 116.25x, r = 0.889, P < 0.05. The activity of Na(+)-K(+)-ATPase on the myocardial cell membranes of the rats with microthrombi was significantly reduced as compared with that of the rats in the control group (P < 0.01). The activity of the Na(+)-K(+)-ATPase was significantly in negative correlation to the rise in the S-T segment of ECG (P < 0.05). This study demonstrates that the above changes are the causes of myocardial injuries in rats with circulatory thrombi.
Insights
High molecular weight dextran induced microthrombi in rats, leading to myocardial injuries. These injuries, indicated by ECG changes, correlated with increased thromboxane B2 and reduced Na(+)-K(+)-ATPase activity.
Area of Science:
- Cardiovascular physiology
- Hematology
- Biochemistry
Background:
- High molecular weight dextran administration can induce changes in blood circulation.
- Microthrombi formation is a potential cause of tissue injury.
- Electrocardiogram (ECG) changes, such as S-T segment elevation, indicate myocardial injury.
Purpose of the Study:
- To investigate the effects of high molecular weight dextran on rat microcirculation and myocardial function.
- To determine the correlation between microthrombi formation, ECG abnormalities, and biochemical markers.
- To assess the impact of microthrombi on myocardial cell membrane Na(+)-K(+)-ATPase activity.
Main Methods:
- SD male rats were intravenously injected with high molecular weight dextran for 4 days.
- Microcirculation was observed using mesentery microscopy.
- ECGs were monitored to detect changes in the S-T segment.
- Blood samples were analyzed for platelet aggregation, plasma TXB2, and 6-K-PGF1 alpha levels.
- Na(+)-K(+)-ATPase activity in myocardial cell membranes was measured.
Main Results:
- Dextran injection led to the formation of microthrombi in venules and capillaries.
- Rats developed elevated S-T segments on ECG, indicative of myocardial injury.
- A significant positive correlation was observed between microthrombi count and S-T segment elevation (r = 0.944, P < 0.01).
- Platelet aggregation increased, accompanied by a decrease in platelet count.
- Plasma TXB2 levels increased significantly, correlating with S-T segment rise (r = 0.889, P < 0.05).
- Na(+)-K(+)-ATPase activity on myocardial cell membranes was significantly reduced (P < 0.01) and negatively correlated with S-T segment rise (P < 0.05).
Conclusions:
- High molecular weight dextran induces microthrombi formation and myocardial injury in rats.
- The observed myocardial injuries are closely linked to the extent of microthrombi and associated biochemical changes.
- Reduced Na(+)-K(+)-ATPase activity may contribute to the observed myocardial dysfunction.