Inhibition of platelet aggregation by rat globin

This study was undertaken to identify and characterize the anti-aggregatory protein factor present in rat polymorphonuclear leukocytes (PMNs) supernatant. Since the purified protein exhibited sequence homology to beta globin, globin was also isolated from rat blood by acid-acetone precipitation and was purified on Superdex-75 column in FPLC. Elution of rat globin on the gel filtration column yielded two peaks of approximately 60 and 30 kDa as observed in the PMNs supernatant. Purity of globin and eluted fractions was further evaluated by SDS-PAGE. Platelet aggregation induced by agonists viz. adenosine-5'-diphosphate (ADP; 2-5 microM), arachidonic acid (AA; 10 microM), A23187 (2.50 microg/ml) was inhibited by globin and the purified fractions. ADP-induced rise in intracellular calcium levels and expression of CD62 on the platelets were reduced by both globin and active fraction of PMNs supernatant. Results obtained suggest that globin or globin-related protein present in the PMNs supernatant inhibits platelet aggregation response.