Relationship Between Vitamin D Supplementation and Platelet Parameters, Platelet Aggregation and Thrombosis in Healthy Adult Male Dogs: A Pilot Study.

Vitamin D has well-documented antithrombotic effects on coagulation system components, and platelet-associated vitamin D receptors (VDR) play an important role. Adenosine 5'-diphosphate (ADP) induced platelet activation, and thrombin induced a change in the VDR shape, allowing it to bind to fibrinogen and stimulate the aggregation cascade. The effect of vitamin D supplementation on thrombosis in dogs has not been investigated. Eight mixed-breed adult male dogs were selected, and oral vitamin D3 at 50 IU/kg was administered for 42 days. Serum levels of 25-hydroxyvitamin D concentration, platelet number, mean platelet volume (MPV), fibrinogen, prothrombin time (PT) and partial thrombin time were measured before treatment (Day 0) and on Days 14, 28 and 42. The results identified a significant reduction in platelet count following the administration of oral vitamin D (p < 0.0001). There was no significant change in ADP-induced platelet aggregation, MPV, fibrinogen, PT and partial thromboplastin time (PTT). The results suggest that oral administration of vitamin D daily at a dose of 50 IU/kg BW for 42 days leads to a reduction in platelet count; larger studies are necessary to confirm the results and to elucidate potential clinical implications.