Endotoxin-induced platelet aggregation in heparinised equine whole blood in vitro.

This research explores how endotoxins can cause platelets in horse blood to clump together, a process heightened by the presence of leukocytes and certain other factors in the blood. The study shows the possibility of managing this process by using certain chemical substances.

Background

• The study tackles the issue of endotoxaemia, a major killer of horses identified by platelet deficiency (Thrombocytopenia) and coagulation problems such as disseminated intravascular coagulopathy, which is often fatal.
• In this context, the researchers explored the role of endotoxins, capable of aggregating or clumping together horse platelets in blood treated with heparin, a common anticoagulant.

Methodology and Findings

• The researchers carried out a series of in vitro, or lab-based, tests where they exposed heparin-treated horse blood to different concentrations of endotoxin.
• The study revealed that endotoxin-induced aggregation (EIA) was reliant on leukocytes, a type of white blood cell, evident from the fact that aggregation did not happen when detoxified endotoxin was used.
• Lipid A, a part of the endotoxin, was found to be vital for this leukocyte-dependent EIA as its absence halted the process.

Role of Other Substances

• The research also evaluated the effect of substances like aspirin, apyrase, and CV3988 on the EIA process.
• While 1 mmol litre-1 of aspirin had no impact on EIA, 40 micrograms ml-1 of apyrase completely terminated it. CV3988 (3 to 30 mumol litre-1), as a competitor of the platelet-activating factor, hindered the response in proportion to its concentrations.

Conclusions

• The study concluded that endotoxin activated horse platelets even at low concentrations through an indirect process. This process involved the usage of calcium, leukocytes, adenine nucleotides (needed for cellular energy), and the platelet-activating factor.
• The presence and concentration of substances such as apyrase and CV3988 could completely halt or reduce the endotoxin-induced platelet aggregation, opening up potential treatment options.