Dextran-70 inhibits equine platelet aggregation induced by PAF but not by other agonists.

This research investigates the effects of 70 kDa dextrans (dextran-70) on equine platelets, finding that they inhibit platelet aggregation induced by platelet-activating factor (PAF) but not by other molecules. This mechanism could partly explain why dextran-70 aids in the treatment of clotting disorders in horses.

Use of Dextrans in Clinical Scenarios

• The research begins by illustrating the pharmaceutical use of dextran-70 as an anti-thrombotic in humans. Anti-thrombotics are medicines that reduce blood clot formation.
• In particular, dextran-70 frustrates platelet action to exert its anti-thrombotic effects.
• The research mentions how dextran-70 has successfully treated thromboembolic colic, a clotting disorder in horses with a reported 90% recovery rate, despite it being rarely used.

Impact of Dextran-70 on Equine Platelets

• The researchers explored the effects of dextran-70 on equine platelets using an in vitro (outside the living body) method.
• The study found immediate effects, with initial activation and shape changes observed in the platelets upon in vitro treatment with dextran-70.
• Notably, the researchers uncovered a dose-dependent inhibition of PAF-induced platelet aggregation by dextran-70. This means the extent of inhibition increased with an increasing concentration of dextran-70.

Specific Impacts of Dextran-70 on PAF-Induced Aggregation

• The researchers observed significant reduction in the rate of platelet aggregation with concentrations of dextran-70 greater than 40 g/l and in the extent of platelet aggregation at concentrations over 50 g/l.
• A pre-incubation step with 60 g/l dextran-70 significantly reduced both the rate and extent of PAF-induced aggregation, regardless of pre-incubation duration.
• The study did not observe any effects on platelet aggregation when the inducing factor was adenosine 5′-diphosphate, collagen, 5-hydroxytryptamine, or U44069, suggesting the inhibitory effect of dextran-70 is specific to PAF.
• Further analysis revealed that dextran-70 acted as a significant noncompetitive inhibitor on PAF-induced platelet aggregation, implying it blocked the function of PAF without competing for its binding site on the platelets.

Implications of the Research

• These experimental findings hint that dextran-70’s anti-thrombotic utility in cases of equine clotting disorders could be due to its inhibitory impact on PAF-induced platelet aggregation.
• The understanding of dextran-70’s mode of action on the aggregation of platelets could aid in creating alternative therapeutic agents for clotting disorders.