Thrombin-induced neuropeptide Y secretion from rat platelets.
AIM
To study the thrombin-induced secretion of platelet neuropeptide Y (NPY) in rats.


METHODS
The platelet aggregation induced by ADP or thrombin was recorded by an aggregometer. NPY in platelet and plasma was measured by radioimmunoassay. The intracellular free Ca2+ ([Ca2+]i) was measured by Fura-2 fluorescent assay.


RESULTS
Thrombin 0.75 or 2.5 kU L-1 increased [Ca2+]i from 119 +/- 8 nmol L-1 to 530 +/- 60 or 1340 +/- 100 nmol L-1, respectively together with the secretion of platelet NPY. Edetic acid 2 mmol L-1 almost abolished the thrombin-induced increases of [Ca2+]i and reduced the NPY secretion by 56% and 30%, respectively. Neither [Ca2+]i increase nor platelet NPY secretion induced by thrombin was affected by verapamil. The thrombin-induced NPY secretion was inhibited by 55%-70% by indometacin or creatine phosphate plus creatine phosphokinase.


CONCLUSION
Thrombin-induced platelet NPY secretion was related to an Ca2+ influx through non-voltage dependent Ca2+ channels and positive feedbacks of arachidonate metabolites or/and released ADP.