Platelet aggregation of quinonoid dihydropteridine reductase knockout mice.

Abstract

Quinonoid dihydropteridine reductase (QDPR) regenerates tetrahydrobiopterin (BH4), an indispensable cofactor for synthesizing catecholamines and serotonin. We evaluated the platelet aggregation of QDPR gene knockout (Qdpr ^-/-) mice. Citrated blood was collected from wild type (Qdpr ^+/+) mice and Qdpr ^-/- mice (OYC35, Lexicon Pharmaceuticals Inc.). Platelet rich plasma (PRP) was obtained by centrifuging the blood, and adjusted platelet count to 250,000/μL. Platelets were stimulated with collagen (3～4 μg/mL) or ADP (5～20 μM) and aggregation was measured by light transmission method for 10 minutes. Intraplatelet serotonin was quantified by high-performance liquid chromatography (HPLC) with electrochemical detection. The Qdpr ^-/- mice significantly decreased the area under the aggregation curve (AUC) stimulated with collagen (Qdpr ^+/+: 6,061±600, Qdpr ^-/-: 3,424±514, p<0.05 by Tukey-Kramer test) and ADP (Qdpr ^+/+: 4,197±295, Qdpr ^-/-: 2,452±266, p<0.05). The intraplatelet serotonin content was significantly decreased in the Qdpr ^-/- mice (Qdpr ^+/+: 48.1±4.0 pmol/10⁶ platelets, Qdpr ^-/-: 22.1±2.8 pmol/10⁶ platelets, p<0.01). These results indicate that the Qdpr ^-/- mice suppresses secondary platelet aggregation via serotonin.