• Despoina Pantazi, Athina Stratou, Evangelia Dounousi, Anastasios Petrou, and Alexandros D Tselepis.
• Med Princ Pract. 2023 Sep 13; 32 (4-5): 242249242-9.

BackgroundSevere variations in osmotic pressure are significant contributors to critical patient morbidity and mortality and might also affect platelet volume. We aimed to investigate possible osmotic-induced changes in mean platelet volume (MPV) and their possible effects on platelet aggregation activity (PLAG).MethodsWe induced experimental variations of serum osmolality in blood samples from healthy volunteers (heparinized whole blood, WB) and isolated platelets (Platelet Rich Plasma, PRP) by adding isotonic, hypertonic, and hypotonic solutions of saline/water (pH = 7.2-7.4). PLAG was tested in WB samples with Impedance Aggregometry (IA) and in PRP samples with Light Transmission Aggregometry (LTA) using three agonists Adenosine Diphosphate (ADP, 10 μΜ), Thrombin Receptor Activating Peptide (TRAP-6, 10 μΜ) and Arachidonic Acid (AA, 500 μΜ). Osmolality was either calculated using a formula or measured directly.ResultsWe found almost identical osmolalities in WB and PRP preparations. Osmotic stress did not produce significant changes in MPV. In IA testing the hypotonic challenge of WB preparations produced significant reductions at 50 % (p = 0.056) (95 % CI: 11.2-2.4, in Ohms) of ADP and at 31 % (p = 0.017) (95 % CI: 13.4-8.6, in Ohms) of TRAP-6 -induced PLAG respectively. In PRP we did not observe any variations in PLAG with LTA.ConclusionsWe conclude that in vitro hypotonic stress of WB samples has an inhibitory effect on the PAR-1 (TRAP-6 induced) pathway and on the P2Y12 (ADP induced) pathway and reflects a distinct in vivo effect of hypo-osmotic stress on WB human platelet preparations.The Author(s). Published by S. Karger AG, Basel.

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