title: P-Selectin and platelet clearance.
abstract: P-selectin is an adhesion receptor for leukocytes expressed by activated platelets and endothelial cells. To assess a possible role of P-selectin in platelet clearance, we adapted an in vivo biotinylation technique in mice. Wild-type and P-selectin-deficient mice were infused with N-hydroxysuccinimido biotin. The survival of biotinylated platelets was followed by flow cytometry after labeling with fluorescent streptavidin. Both wild-type and P-selectin-deficient platelets presented identical life spans of about 4.7 days, suggesting that P-selectin does not play a role in platelet turnover. When biotinylated platelets were isolated, activated with thrombin, and reinjected into mice, the rate of platelet clearance was unchanged. In contrast, storage of platelets at 4 degreesC caused a significant reduction in their life span in vivo but again no significant differences were observed between the two genotypes. The infused thrombin-activated platelets rapidly lost their surface P-selectin in circulation, and this loss was accompanied by the simultaneous appearance of a 100-kD P-selectin fragment in the plasma. This observation suggests that the platelet membrane P-selectin was shed by cleavage. In conclusion, this study shows that P-selectin, despite its binding to leukocytes, does not mediate platelet clearance. However, the generation of a soluble form of P-selectin on platelet activation may have biological implications in modulating leukocyte recruitment or thrombus growth.
authors.affiliation: The Center for Blood Research, Harvard Medical School, Boston, MA, USA.
authors.forename: G
authors.initials: G
authors.lastname: Berger
authors.forename: D W
authors.initials: DW
authors.lastname: Hartwell
authors.forename: D D
authors.initials: DD
authors.lastname: Wagner
mesh_terms: D000375:Aging / Q000097:blood; D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D001793:Blood Preservation; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019007:P-Selectin / Q000502:physiology*; D015539:Platelet Activation
chemical_list: D019007:P-Selectin