[Platelet neuropeptide Y and its vasoconstriction effect in rat].

Specific radioimmunoassay showed that in rat neuropeptide Y (NPY) immuno-reactivities (IR) in platelets and platelet rich plasma (PRP) were respectively 90 +/- 16 ng/10(7) platelets and 93 +/- 19 ng/ml. Both values were much greater than those in the plasma (1.2 +/- 0.1 ng/ml, P < 0.001) and platelet poor plasma (PPP) (1.7 +/- 0.3 ng/ml, P < 0.001). The NPY-IR in rat platelets eluted at the same position as authentic NPY on reverse phase HPLC. The NPY-IR in the platelets prepared from the PRP aggregated maximally by collagen reduced to 34 +/- 5 ng/10(7) platelets, while the NPY-IR in the PPP prepared from the same PRP increased to 26 +/- 4 ng/ml. PPP 1.6 ml prepared from the aggregated PRP induced contraction of isolated rat caudal arteries with the maximal tension of 380 +/- 80 mg; while the maximal contraction induced by 1.6 ml of the same PPP pretreated with NPY anti-serum was only 190 +/- 40 mg (P < 0.001). Authentic NPY 1 nmol/L did not cause any contraction. The results indicate that rat platelets contain a high concentration of NPY, which can be released during irreversible platelet aggregation. The NPY released can potentiate vasoconstriction responses induced by co-released substances during platelet aggregation.