IMMUNOREACTIVE NEUROPEPTIDE-Y (NPY) IN PLASMA AND PLATELETS OF RAT AND MOUSE STRAINS AND HUMAN VOLUNTEERS

Immunoreactive-neuropeptide Y (i-NPY) is present in platelets of rats, and has recently been demonstrated to be authentic rat NPY based on i ts amino acid sequence. This potent vasoconstrictor and putative smoot h muscle mitogen is released during platelet activation, suggesting a role in platelet-vascular interactions. We have now extended this work to several strains of rats and mice, and humans of both sexes. Among mice, strains in which NPY mRNA has been demonstrated in megakaryocyte s have markedly higher levels of i-NPY (0.63-1.11 pmol/ml in NZB/B1NJ, NZBWF1/J, BXSB/MpJYaa, BALB/cJ) in platelet rich plasma (PRP) than ot her strains (DBA/2J, CBA/J, C3H/HeJ, MRL/MpJ-lpr, C57BL/6J; each <0.02 pmol/ml). In rats, high content of i-NPY was observed in PRP and plat elets of all strains examined (Sprague-Dawley, Wistar, Wistar Kyoto). i-NPY level was 30.6, 3.7 and 10.1 pmol/ml in PRP of the three strains , respectively. In humans, low levels of i-NPY occur in plasma and pla telet fractions compared to rodents (0.069 and 0.048 pmol/ml in male a nd female PRP, respectively), but they, too, have greater i-NPY in pla telet rich plasma and platelets than in platelet poor plasma. Assuming this is authentic NPY, platelet-derived NPY might have a role in path ophysiological states involving activation of platelets in humans.