In vivo tracking of platelets: circulating degranulated platelets rapidly lose surface P-selectin but continue to circulate and function
Department of Pediatrics; Department of Surgery
Animals; Antibodies, Monoclonal; Blood Platelets; Blood Transfusion, Autologous; Flow Cytometry; Fluorescent Dyes; Male; Organic Chemicals; P-Selectin; Papio; Platelet Activation; Platelet Glycoprotein GPIIb-IIIa Complex; Platelet Transfusion; Thrombin; Time Factors
Life Sciences | Medicine and Health Sciences
To examine the hypothesis that surface P-selectin-positive (degranulated) platelets are rapidly cleared from the circulation, we developed novel methods for tracking of platelets and measurement of platelet function in vivo. Washed platelets prepared from nonhuman primates (baboons) were labeled with PKH2 (a lipophilic fluorescent dye), thrombin-activated, washed, and reinfused into the same baboons. Three-color whole blood flow cytometry was used to simultaneously (i) identify platelets with a mAb directed against glycoprotein (GP)IIb-IIIa (integrin alpha 11b beta 3), (ii) distinguish infused platelets by their PKH2 fluorescence, and (iii) analyze platelet function with mAbs. Two hours after infusion of autologous thrombin-activated platelets (P-selectin-positive, PKH2-labeled), 95 +/- 1% (mean +/- SEM, n = 5) of the circulating PKH2-labeled platelets had become P-selectin-negative. Compared with platelets not activated with thrombin preinfusion, the recovery of these circulating PKH2-labeled, P-selectin-negative platelets was similar 24 h after infusion and only slightly less 48 h after infusion. The loss of platelet surface P-selectin was fully accounted for by a 67.1 +/- 16.7 ng/ml increase in the plasma concentration of soluble P-selectin. The circulating PKH2-labeled, P-selectin-negative platelets were still able to function in vivo, as determined by their (i) participation in platelet aggregates emerging from a bleeding time wound, (ii) binding to Dacron in an arteriovenous shunt, (iii) binding of mAb PAC1 (directed against the fibrinogen binding site on GPIIb-IIIa), and (iv) generation of procoagulant platelet-derived microparticles. In summary, (i) circulating degranulated platelets rapidly lose surface P-selectin to the plasma pool, but continue to circulate and function; and (ii) we have developed novel three-color whole blood flow cytometric methods for tracking of platelets and measurement of platelet function in vivo.
Proc Natl Acad Sci U S A. 1996 Oct 15;93(21):11877-82.
Proceedings of the National Academy of Sciences of the United States of America
Michelson, Alan D.; Barnard, Marc R.; Hechtman, Herbert B.; Macgregor, Hollace; Connolly, Raymond J.; Loscalzo, Joseph; and Valeri, C. Robert, "In vivo tracking of platelets: circulating degranulated platelets rapidly lose surface P-selectin but continue to circulate and function" (1996). Open Access Articles. 1802.